Old Adam Francis Plummer would be proud to know that the first survey of Prince George's County's black historical sites was completed recently in the same building where, as an industrious young slave, he secretly learned to read and write more than 100 years ago.

Plummer, who died in 1905, was a house slave to George H. Calvert, Lord Baltimore, on the plantation called "Riverdale," from which the town of Riverdale takes its name.

The Calvert Mansion at 4811 Riverdale Rd., where Plummer made shoes, among other chores, was included in the July 1981 listing of the Prince George's Historic Sites and Districts plan, along with 159 other buildings and places.

But the slave quarters of the Calvert mansion and at least 60 other places significant in the history of blacks in Prince George's were not included in the plan. The sites of black historical interest were left out because they did not involve "prominent individuals and known historic events," researcher Susan Pearl of the history division of the Maryland-National Capital Park and Planning Commission said as she explained the criteria used by authors of the plan.

Prince George's always has had a high percentage of black residents--from the antebellum period when the slave and free black population was about 50 percent of the census, to as recently as 1900 when the county was 40 percent black. In the following decades, the county's white population grew and became the majority. Now the pendulum is swinging back and, according to the 1980 Census, blacks are 37 percent of the county's population.

Most of the black historical sites mark the beginnings of churches, schools and meeting places established by blacks for their survival and struggle to advance in the first generation following slavery.

Pearl and fellow researcher Bianca Floyd, working with funds from the Prince George's County Council and the Maryland Historical Trust, soon found that sites of black historic importance in the county existed side by side with important white sites.

It simply required extensive digging through land records, birth and death certificates, the records of the Freedmen's Bureau that oversaw the welfare of blacks during Reconstruction and almost any other type of record of the period following the Civil War.

"We spent a lot of time traipsing through cemeteries," Floyd said.

For example, the Riverdale slave quarters--where Floyd and Pearl have their offices--sits next to the Calvert Mansion, now maintained by the county parks department. According to Pearl, the two-story brick building covered with yellow stucco is the most substantial of the few remaining slave quarters in Prince George's County. It acquires added importance from the fact that Nellie Arnold Plummer, using a rare slave diary kept by her father from 1841 to 1905, wrote a biography in 1927 of her father's life as a slave and as a free man.

Now that the sites have been researched, their owners or private citizens can request that they be added to the Historic Sites and Districts plan. Inclusion in the plan grants tax incentives for restoration and maintenance of the site, as well as protection from harmful development.

"The thing that surprised me most is that, despite what a lot of people think, black people had a lot to do with the establishment of this county. Not just as slaves, but as freed men," said Floyd, who grew up in Prince George's.

In 1908, for example, the Lincoln Land and Improvement Co. bought 200 acres of land just north of George Palmer Highway and Glenn Dale Road with the purpose of establishing, "without restriction as to race, but primarily by, for and of colored persons, a community with its own municipal government, schools, churches, commercial and industrial life," according to a 1915 article by Thomas J. Calloway, a black educator, land developer and lawyer who was general manager of the company.

Calloway gained fame upon his appointment as a U.S. representative to the Paris Exposition of 1900, where he was responsible for a photographic exhibit of black industrial education in the United States. Calloway, who had an office in the District of Columbia, was associated with such major black historical figures as W.E.B. Dubois, Mary Church Terrell and A. Philip Randolph.

The Lincoln company's land was divided into small lots and sold to black families from Pennsylvania to Virginia. The streets laid out were from 50 to 70 feet wide, spacious by the standards of the day. Lincoln was home to many prominent black craftsmen, professionals, clergymen and businessmen. It had its own water system and school and, at its center, the Seaton Memorial African Methodist Episcopal Church.

The church was named after Lincoln resident Dr. Daniel P. Seaton, who turned from practicing medicine to theological studies and wrote a book on Palestine called "The Land of Promise." To this day, the church remains near the heart of the small, predominantly black community.

The year before the land was bought, William Sidney Pittman, a black architect and son-in-law of perhaps the most prominent black man of the era, Booker T. Washington, built a home at 505 Eastern Ave. in Fairmount Heights. While he lived there, his black architectural firm became the first to win a federal contract--to build the $70,000 Negro Building at the National Tercentennial Exposition at Jamestown, Va., in 1907.

Pittman also founded the Fairmount Heights Improvement Co. to develop the town as an alternative to inner-city living in the District. Pittman, with the sponsorship of Washington, received many commissions during his stay in Fairmount Heights. The Pittmans later moved to Dallas but did not prosper there, and Pittman later served time in prison for extortion, according to University of Maryland professor Lewis Harlan, a Booker T. Washington scholar.

But the house still stands at 505 Eastern Ave., and Fairmount Heights remains a thriving black community.

While the overall percentage of black residents in Prince George's fell as low as 13 percent during the 1960s, there have always been a number of black enclaves scattered throughout the county. The only structures remaining from many of these communities are one- or two-room school buildings, usually built during the 1920s and 1930s, all with a similar design, according to researcher Pearl.

One of the best examples of an early black school, church and social hall still standing is the Rebecca Lodge No. 6, also known as Abraham Hall, on Old Muirkirk Road in Muirkirk.

The Muirkirk community grew from black families employed at the Muirkirk Iron Furnace, which manufactured cannon during the Civil War. Abraham Hall was built in 1888 by members of the Benevolent Sons and Daughters of Abraham. The benevolent societies provided financial assistance in emergencies, death benefits and other insurance-type benefits that otherwise were not available to blacks at the time.