In the late 1600s, the colony of Maryland was in turmoil. England's war with France was spreading to the New World, relations with the Indians were strained and the rule of the Calverts, the Lords of Baltimore, had been rescinded, a result of the Revolution of 1688, which placed the Protestant rulers William and Mary on the throne of England and left the solidly Catholic Calverts without royal patronage.

The Maryland colony was now a royal province, and its new leaders turned their attention to reorganizing the government. The General Assembly quickly moved the capital from the Catholic stronghold of St. Mary's City to Anne Arundell Towne (soon to be renamed Annapolis), and then set about chartering a new county. An act was passed that set April 23, 1696, as the date for the creation of a county to be named after Denmark's Prince George, the husband of Princess Anne, next in line for the throne of England. The county was an immense, unmapped area, stretching from the Potomac River to the border of Pennsylvania, from the county known as Annarundell west to a vague point somewhere in the vast, unexplored forests of the frontier. Three hundred years later, Prince George's County is smaller than it was at birth, reduced by 1748 to almost its present boundaries. Since those days the county has been well-mapped but not always well-explored, even by those who live within it or around it. Overshadowed by the rebuilt colonial capital of St. Mary's City and the charming 18th-century streets of Annapolis and Frederick, Prince George's County just doesn't get, well, any respect.

It's not because there isn't anything to see: Prince George's County has more than 1,200 historic sites on the list compiled by the Maryland Historic Trust. Seventy-two buildings are on the National Register of Historic Places. One person who knows well the county's hidden charms is Donald Creveling, an archaeologist for the Maryland-National Capital Park and Planning Commission (M-NCPPC), who says, 'The architecture and landscape here is a constant reminder of our shared past. From Bowie south to Aquasco, there are remnants of almost every century since the colonists were first here.'

This 'shared past' is rich with historic events. It was in Prince George's County that the British launched their attack on Washington in 1814. It was in College Park that the military first learned to fly and helicopters first whirled off the ground. It was in Beltsville that agricultural research improved the food on our tables and discovered the key to mass production of antibiotics. It was in Riverdale that one of the first telegraph messages was received. It was in Greenbelt that urban planning took a step forward and where humans began to explore the deepest edges of space.

The seeds of the vibrant community were sown in 1696 with the county's creation. The move lured ever more settlers to virgin land that held great promise. Colonial planters amassed vast plantations and great wealth from golden tobacco leaves and black slaves. This wealth led to the creation of an aristocratic culture whose pastimes included horse racing, fox hunting, cricket, theatricals and music. Ships as large as 400 tons carried hogsheads of tobacco to London and brought back wines from Madeira and finished goods from England. For a time, the wealth created by the English demand for tobacco turned Bladensburg, Upper Marlborough (as it was spelled in those days) and other Maryland river cities into international seaports, with shops selling tools, teas and finery imported from the finest shops in Britain.

Despite the citizenry's ties, emotionally and financially, to England, many of the gentry willingly joined the fight for independence in 1776. And after freedom was won, Prince George's County provided most of the land that was needed to create the national capital in the new District of Columbia and, from 1790 to 1800, served as the governing body of the new federal enclave. Indeed, the Capitol, the Supreme Court and the White House all now sit on land that once was part of Prince George's County.

This proximity to the capital did not go unnoticed by the British. In 1814, they sailed a war fleet up the Patuxent River, landed troops at Benedict, in Charles County just south of the Prince George's border, and marched them through Nottingham, Upper Marlborough and Forestville on their way to Washington. The new nation's army, a poorly equipped force that was plagued by indecisive leadership, marched to Bladensburg to confront the invaders and was quickly routed. The Redcoats, their way to Washington unimpeded, sacked the capital city before retracing their steps back into Maryland.

An incident during their return set the stage for one of those quirky footnotes to history. William Beanes, a patriot and highly respected physician in Upper Marlborough, managed to capture a few British stragglers, an act that so angered the British general, Sir Robert Ross, that he took Beanes prisoner with him as he sailed to Baltimore. A Frederick attorney heard of Beanes's capture and went to Baltimore to plead for his release. The attorney, a chap named Francis Scott Key, succeeded in his plea but was told that he and Beanes must remain on the ship until after the bombardment of Fort McHenry. 'By the dawn's early light,' Key could see that the attack had failed, inspiring him to write a poem that later became our national anthem.

The peace that came after that war allowed the farmers of the county to turn again to the soil, and agriculture quickly became the backbone of the economy. Tobacco plants soon wore out the land, so farmers began experimenting with new crops and new methods of agriculture. In 1817, Maryland's first agricultural society was formed in Prince George's County, attracting Charles Benedict Calvert, a descendant of the founding family of the colony, and other prominent planters. Calvert's role was vital. He donated the land that became the Maryland Agricultural College, the forerunner of the University of Maryland, and while serving in Congress, he sponsored the legislation that founded the federal Department of Agriculture. He was also a strong supporter of an inventor named Samuel Morse, who tested his telegraph device in 1844 by sending a message from Washington to Calvert's home in Riverdale.

Of course, plantation life had a grim side: slavery. By 1860, 60 percent of the county's residents were black, and 90 percent of those residents were slaves. Despite being a majority of the population for so many years, the heritage of those black residents is barely visible today. 'The problem is that so much of it from 1900 back is gone,' said Susan Pearl, an M-NCPPC research/architectural historian who is compiling a list of black history sites in the county. Creveling, the M-NCPPC archaeologist, explained, 'The buildings we have from the 18th and 19th centuries are primarily made of brick,' a building material favored by the upper classes, who were about the only ones who could afford it. 'Brick is a very durable building material. When you are speaking of slaves or tenant farmers, generally the housing was of a more ephemeral nature.'

Still, several sites reflect the black heritage of the county. The Cherry Hill Cemetery in Riverdale is believed to hold the graves of 12 slaves or freed blacks, and the Dorsey Chapel, a small frame church built around 1900 in Glenn Dale, is an example of the role small churches played as social and cultural centers for the county's black residents. A third site, a brick-foundationed slave quarters in the Lake Arbor subdivision not far from USAir Arena, is being excavated by Creveling, who hopes to open the site as a public park later this year.

After the Civil War, the county remained a primarily agricultural area, with the industrial revolution bypassing much of the county. What little industry there was -- a few small iron forges in the north end of the county, and some busy cotton and grain mills in Laurel -- predated that conflict.

Abolition also meant the end to the large plantations, which were not viable economically without slave labor. Smaller farms become more common, many of them owned by freed slaves. And by the end of the 19th century, there was a new force affecting the county: the federal government. The capital city had grown along with the still-expanding nation. Residential and commercial neighborhoods slowly spread east into the county, with new towns popping up along the border with the District.

The closeness to the capital, which the British had exploited in 1814, turned out to be more profitable in the 1900s. College Park Airport, the oldest continuously operating airport in the nation, was where military officers were taught to fly in 1909 by the Wright Brothers. A year later, the Agricultural Research Center opened in Beltsville and quickly began reshaping what we put on our dinner table and into our medicine cabinets.

Not all the advances were scientific or technological. In the 1930s, the Roosevelt administration launched an experiment in urban planning, with the goal of creating a model community. Three such cities were created, one in Wisconsin, one in Ohio and the third in Prince George's County. Greenbelt was a success for the government, intellectually if not financially, and was the forerunner of such privately planned communities as Reston and Columbia.

World War II brought more change. Andrews Air Force Base became a major military air transport center, and the base for the pilots and planes that fly the president and other Washington VIPs. And that curious World War II weapon, the rocket, led to the creation in 1959 of the NASA/Goddard Space Flight Center, which today builds and controls satellites exploring the Earth, operates the Hubble Space Telescope, and serves as the communications center for all shuttle flights.

Those are a lot of accomplishments for one county, even if it did take three centuries to make them. And as the fourth century begins, perhaps it's time to discover a place that archaeologist Creveling calls 'the best kept secret in Maryland.'

CELEBRATING THE PAST

Prince George's County commemorates its 300th birthday on Tuesday with a parade and a grand gala. The festivities in Upper Marlboro begin at 11:30 with a concert by the U.S. Air Force Band at the County Courthouse, 14735 Main St., followed by speeches and presentations by county and state dignitaries. At 12:35, an Air Force flyover will signal the start of a parade of military and ROTC units, marching bands and other groups along Main Street, starting at Gov. Oden Bowie Drive. For more information, call 301/322-1996.

The black-tie Tricentennial Gala is Tuesday evening at the University of Maryland's Cole Field House. Tickets are $50 and up for an evening that includes dinner, dancing and entertainment. Doc Scantlin and his Imperial Palms Orchestra, Gladys Knight, the Hubcaps, Spur of the Moment and Day Ta Day will entertain. For more information, call 301/468-1695.

A free Tricentennial Passport, a visitors guide to 16 historic sites in the county, is available at most of the sites listed below and at the Maryland-National Capital Park and Planning Commission offices at 6600 Kenilworth Ave., Riverdale. Visitors using the booklet can enter a contest for a grand prize of a trip for two to England or other prizes by having their Tricentennial Passport stamped at the historic sites listed in the booklet. Other prizes are passes to M-NCPPC facilities, golf courses, theater and sports complexes, souvenir items and history publications. The contest runs through Dec. 31, 1996. For more information about all Tricentennial activities or the contest, call 301/322-1996.

Here is a list of historic sites in the county that welcome visitors:

AGRICULTURAL RESEARCH SERVICE National Visitor Center, on Powder Mill Road between Edmonston Road and the Baltimore-Washington Parkway. Have you ever wondered what goes on at the 7,200-acre Beltsville Agricultural Research Center? And just how they are spending your tax money? The visitor center has the answers, with exhibits recounting the development of modern food and farming techniques. The service played a vital role in the creation of small, plump turkeys, instant mashed potatoes and frozen orange juice made from concentrate. Its most lasting contribution may have been the discovery of a process to produce huge quantities of penicillin -- using a moldy cantaloupe found in a local market -- a discovery that built the foundation of the modern pharmaceutical industry. The center is in what is called the Log Lodge, a 60-year-old building modeled after the rustic lodges of Yellowstone National Park. The center is open from 8 to 5 daily. Tours are offered from 8 to 4:30 by appointment only. Call 301/504-8483 or 301/504-9403.

BELAIR MANSION AND STABLE MUSEUMS -- 12207 Tulip Grove Dr., Bowie. Samuel Ogle, provincial governor of Maryland in the mid-18th century, built this majestic Georgian mansion in the 1740s. His son, Benjamin Ogle, also lived there while serving as governor from 1798 to 1801. The mansion was later expanded by the Woodward family, who operated a thoroughbred farm that produced two triple Crown winners (Omaha and Gallant Fox). The mansion served as the Bowie City Hall from 1964 to 1978, and is now a museum featuring exhibits and furnishings from the 1740s through the 1950s. The mansion is open Sundays noon to 4 year-round. The stables are open Sundays 1 to 4 in May, June, September and October. Admission to the mansion is a $3 donation; admission to the stables is free; call 301/805-5029.

CHERRY HILL CEMETERY -- 6821 Ingraham St.,Riverdale. This burial ground is believed to be the final resting place of the family of Josiah Adams and his relatives, who are thought to have been slaves or descendants of slaves on the nearby Riversdale and Calvert estates. Adams was a gardener on the Riversdale Plantation and after abolition he became a farmer. He was buried there in 1894. Archaeologists conducted examinations of the site and found 12 graves, which are now marked by small, rust-colored slabs of unfinished ironstone. The names of those buried here are not known. From Kenilworth Avenue and Route 410 (East-West Highway), take Route 410 east under the Baltimore-Washington Parkway, turn right on 66th Avenue, then left on Oliver Street. When Oliver dead-ends at Ingraham, turn right and drive 50 yards to the cemetery, which is on the left. For more information, call Donald Creveling at M-NCPPC at 301/218-9637.

COLLEGE PARK AIRPORT MUSEUM --1909 Cpl. Frank Scott Dr., College Park. The oldest continuously operating airport in the nation was where the Wright Brothers first taught military officers to fly, where the first helicopter flew and the birthplace of air mail service. The museum displays photographs, some dating back to those first years, as well as artifacts, models and other memorabilia recalling the events in one of the cradles of aviation. Open Wednesday through Friday 11 to 3, weekends 11 to 5. Free; call 301/864-6029 (TDD: 301/864-4765).

DARNALL'S CHANCE -- 14800 Gov. Oden Bowie Dr., Upper Marlboro. Built around 1704, this early Georgian structure may be the oldest building in the county. The brick house, once hidden behind a mid-19th century stucco facade, was built by Henry Darnall, a wealthy landowner and merchant. This was not Darnall's main house, which was his plantation named Woodyard, whose ruins are near where Andrews Air Force Base is now; it is believed he used the Upper Marlboro house when the courts and markets were held in Upper Marlboro. Darnall's granddaughter, Elizabeth, inherited the property. She and her husband, Daniel Carroll, had two sons, who were probably born here: Daniel Carroll, signer of the Constitution, and John Carroll, the first Catholic bishop in America. Little of the original structure remains today in the house. The upstairs bedrooms display dioramas on the Darnall family and Maryland history. Historians believe the basement was once used as slave quarters. One room is furnished with 18th-century furniture. In the back yard, a large brick burial vault was discovered in 1990, containing the skeletons of six adults and three children. Their identity is unknown, but they are believed to be from the family of Lettice Lee, who owned the property in the late 1700s. If you visit here, walk out the driveway, turn right and follow the path around the lake to the low hill next to the Sheriff's Office. The small, fenced cemetery there contains the grave of William Beanes, a physician and patriot whose capture by the British in 1814 inadvertently led to the events that inspired Francis Scott Key to compose the words that became our national anthem. Darnall's Chance is open on Fridays 11 to 3 and Sundays noon to 4; open at other times by appointment. Admission is $3, $2 seniors, students and members of tour groups; call 301/952-8010.

DORSEY CHAPEL -- 10704 Brookland Rd., Glenn Dale. The small, white frame structure was built in 1900 as the Brookland Methodist Episcopal Church, though it was better known as simply the Dorsey Chapel. The church served as a center of the African American community in the area and was in use until 1971. Now owned by the M-NCPPC, the chapel will reopen in May and be open the first and third Sundays of the month from 1 to 4. Admission fees have not been set yet, but they will be nominal; call 301/464-5291.

DUVALL TOOL MUSEUM -- Patuxent River Park, 16000 Croom Airport Rd., Upper Marlboro. Have you ever seen a sausage stuffer? How about a potato-chip maker or calf weaner? These and more than 1,000 other 19th-century tools and items were collected by W. Henry Duvall, an electrician and farmer who grew up in the area near the museum. Visitors who have nightmares about dentists may want to avoid the pedal-operated drill in the exhibit on 19th-century dentistry. Open Sundays 1 to 4, other times by reservation. Free; call 301/627-6074.

FORT WASHINGTON PARK --13551 Fort Washington Rd., Fort Washington. This fort was completed in1824 to protect the harbors of Alexandria, Georgetown and Washington, and was well-equipped for battle -- 60 cannons inside, 25 outside -- but never was involved in combat. Now part of the National Park Service, the massive masonry-and-brick fortification is the site of many historic reenactments. The next is on May 12, when living history interpreters re-create the life of Civil War soldiers. Stop by the commandant's headquarters (the large yellow house) for information on the fort's history. Also popular are the torchlight tours held at night at the fort. The first this year is on June 22. The fort and park are open daily 9 to 5. Admission is $4 per car. There is no charge for the torchlight tours at this time, but park officials are considering fees for evening activities. Call 301/763-4600.

GREENBELT MUSEUM -- 10-B Crescent Rd., Greenbelt. This original structure in what was the 1930s version of utopia -- a federally planned town built around a common park -- features furniture and household appliances created for the homes in Greenbelt, as well as other objects of historic and artistic interest. Greenbelt was created in the early 1930s by the Roosevelt administration's Resettlement Administration. Two thousand homes were built and quickly filled with families. Some museum exhibits are displayed in the Community Center across the street at 15 Crescent Rd. Open Sundays 1 to 5. Free; call 301/474-1936.

LAUREL MUSEUM. Ninth and Main streets, Laurel. This restored mid-18th-century, three-story brick-and-stone millworkers' house is believed to be the oldest structure in Laurel. The building once housed workers for a cotton duck mill in town. It is now a city-owned museum operated by the Laurel History Society, with exhibits on two centuries of life in Laurel. The museum opens for the first time April 28 and will welcome visitors through December on Wednesdays from 10 to 2 and on the first Sunday of each month from 1 to 4. Free; call 301/725-7975.

MARIETTA MANSION -- 5626 BellStation Rd., Glenn Dale. U.S. Supreme Court Justice Gabriel Duvall built this federal style brick home in 1812. Two outbuildings -- the judge's law office and a two-story building that was a harness room and root cellar --are original to the estate. The building is now the headquarters of the Prince George's County Historical Society. Open Fridays 11 to 3, Sundays noon to 4. Admission is $3, $2 seniors and $1 students; call 301/464-5291 (TDD: 301/779-5321).

MONTPELIER MANSION -- Route 197 and Muirkirk Rd., Laurel. Montpelier -- one of Maryland's finest examples of 18th-century Georgian architecture -- was built around 1783 by Maj. Thomas Snowden, an officer in the Revolutionary Army whose family operated an ironworks. Snowden was a gregarious host, whose guests included both George Washington and Abigail Adams, wife of John Adams, who described the mansion as a 'Large, Handsome, Elegant House, where I was received with what we might term true English hospitality.' Washington, on his way to Philadelphia for a Constitutional Convention, noted in his diary on May 5, 1787, that he was unwell during his stay at Montpelier, 'feeling very severely a violent hd. ache & sick stomach...' Costumed guides offer tours of the 12-room mansion, which has been restored and furnished in the period style. The Montpelier Cultural Arts Center, adjacent to the mansion, is home to 20 artists, who rent space to work and sell their creations in textiles, sculptures, paintings, baskets and prints. The arts center is now showing the exhibit 'Prince George's Portraits,' a collection of photographs of county residents over the years. The exhibit continues through May 30. The Montpelier Spring Festival of music and art is May 5 from noon to 6. The mansion is open Wednesdays and Sundays 11 to 4; the center is open daily 10 to 5. Admission to the mansion is $3, $2 seniors and $1 children. For information, call 301/953-1376 (TDD: 301/490-2329) for the mansion or 301/953-1993 for the arts center.

NASA/GODDARD SPACE FLIGHT VISITOR CENTER -- Soil Conservation Road, Greenbelt. This space center controls the Hubble Space Telescope and other important space and Earth research satellite missions. The center offers exhibits and interactive computer displays that allow visitors to test spacecraft component design and learn how satellites are controlled. Guided tours are offered at 11:30 and 2:30 Monday through Saturday. Visitors on these tours see the NASA control room and the Hubble Space Telescope control center. On the first and third Sundays of each month, guided tours are offered at 11, followed by model rocket launches at 1. On the second and fourth Sundays of each month, bus tours are offered at 11 and 2. These tours take visitors to the huge 'clean' rooms where satellite and shuttle components are tested and assembled and to the testing and evaluation facility for those components. The center hosts a Goddard Community Day April 28, with model rocket launches, living-in-space demonstrations, tours of the center and other activities. The center is open daily 9 to 4. Free; call 301/286-8981 (TDD: 301/286-8103).

NATIONAL COLONIAL FARM -- Bryan Point Rd., Accokeek. Located in the 4,500-acre Piscataway Park directly across the Potomac River from Mount Vernon, this privately operated site is a re-created 18th-century farm with living history interpreters who feed the animals, tend the gardens and work the land. The farm has a colonial farmhouse, an original tobacco barn, and breeds of colonial-era livestock -- Devonshire cattle, for example -- and types of plants -- red may wheat, American chestnut and several varieties of tobacco -- common to colonial farms. Take Route 210 south 10 miles from the Beltway and turn right on Bryan Point Road. Open Tuesday through Sunday 10 to 4:30. Admission is $2, 50 cents for children 3 through 12 (younger free; maximum $5 per family); call 301/283-2113.

RIVERSDALE MANSION -- 4811 Riverdale Rd., Riverdale. This mansion was built in 1801 by Belgian financier Henri Joseph Stier, who had fled the turmoil of the French Revolution. The manor house, a modified copy of Stier's Chateau du Mick in Belgium, is constructed of brick covered with cream-colored stucco, an unusual construction technique that is said to have reminded Stier of homes in Europe. Stier's daughter, Rosalie, married George Calvert, a descendant of the founding family of Maryland. Their son, Charles Benedict Calvert, was a prominent horticulturist whose advances in farming techniques won respect around the world. He donated the land for the Maryland Agricultural College in 1856, which later became the state university. He also served in Congress and sponsored the congressional legislation that established the U.S. Department of Agriculture. Calvert also was a strong supporter of Samuel Morse, who invented the telegraph and, on April 9, 1844, successfully tested his device by transmitting a message from the nation's capital to Riversdale. This test came 45 days before the more celebrated event when Morse sent the message 'What hath God wrought!' from Washington to Baltimore on May 24, 1844. The exhibit 'Something's Brewing: Beer and Winemaking in the 19th Century,' runs through April 28, with tastings on April 28. Open Fridays 11 to 3 and Sundays noon to 4. Admission is $3, $2 seniors and $1 students; call 301/864-0420.

SURRATT HOUSE MUSEUM -- 9118 Brandywine Rd., Clinton. Built in 1825, this two-story blood-red home was owned by Mary Surratt, who was hanged for her role in the conspiracy to assassinate President Lincoln. The house and tavern she and her family owned are open to visitors. Exhibits include rifles hidden in the house by the plotters and artifacts from 19th-century life. Special events include 'All Dressed Up,' a display of 19th-century fashions (May 30-Sept. 1), a reenactment of a 'Civil War Wedding' (June 23) and 'John Wilkes Booth Escape Tours' (Sept. 7 and 14 and Oct. 5, 12 and 19). The Surratt House also sponsors special Prince George's County Tricentennial Tours this Tuesday and on May 29, Sept. 25 and Oct. 29. The day-long tours focus on the history of the county and cost $30, which includes lunch and transportation. Tour itineraries vary; call for details. Open Thursdays and Fridays from 11 to 3, Saturdays and Sundays from noon to 4. Admission is $3, $2 seniors and $1 students ages 5-18 (younger free); call 301/868-1121 (voice and TDD).