Local Area Info: Adelphi, Maryland

Adelphi is an unincorporated area and census-designated place in Prince George's County, Maryland. The population was 15,086 at the 2010 United States Census. Adelphi includes the following subdivisions; Adelphi, Adelphi Park, Adelphi Hills, Adelphi Terrace, Adelphi Village, Buck Lodge, Chatham, Cool Spring Terrace, Hillandale Forest, Knollwood, Lewiston, and White Oak Manor.

The unincorporated Adelphi community takes its name from the historic Adelphi Mill, established in 1796 along the Northwest Branch of the Anacostia River. The Adelphi Mill is administered by the Maryland-National Capital Park and Planning Commission and continues to attract visitors and can be rented for special functions. During the 19th century, George Washington Riggs acquired much of the area northeast of Washington, D.C., as his Green Hill estate in the Chillum Manor district. That estate included present-day Adelphi. In the early 1920s, part of the area was acquired by Leander McCormick-Goodhart as part of his Langley Park estate. Labor organizer Mary Harris "Mother" Jones died in 1930, at the farm of Walter and Lillie May Burgess near Powder Mill and Riggs Roads in present-day Adelphi. A marker was erected by the Maryland State Highway Administration commemorating Mother Jones at her death site. Unlike its nearby neighbors Hyattsville and College Park, the area remained relatively undeveloped until immediately following World War II. At that time, subdivisions quickly developed. To distinguish it from the other neighboring unincorporated communities of Lewisdale and Langley Park, the growing subdivisions banded together in the mid-1950s and adopted the name "Adelphi" to reflect their commitment to the preservation of the historic mill of the same name. These subdivisions now include Adelphi Park, Chatham, Cool Spring Terrace, Adelphi, Buck Lodge, White Oak Manor, Hillandale Forest, Knollwood, and Lewiston. A community focal point that originally developed in the late 1950s is the Adelphi Pool, a private pool in the Adelphi neighborhood, located next to George Washington Cemetery on Riggs Road. In order to swim at the Adelphi Pool, people are required to purchase a membership. Non-members of the Adelphi pool may swim, provided they are accompanied with a member. However, in order for non-members to enjoy this privilege, they must fork out a small fee. The Adelphi pool, like most other private swimming pools, does offer swimming lessons and also features swim teams which compete against each other. Two notable features about the Adelphi Pool, is that it features a long water slide, as well as a small basketball hoop.

In 1971, the Harry Diamond Laboratories was established on 137 acres (0.55 km2) in the northern part of Adelphi. That facility continues as the Adelphi Laboratory Center, Army Research Laboratory (ARL), the U.S. Army's corporate research laboratory. Other adjacent federal facilities include the National Archives at College Park and headquarters of the Food and Drug Administration.