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Adelphi, Maryland facts for kids

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Adelphi, Maryland
The Adelphi Mill in July 2007
The Adelphi Mill in July 2007
Location of Adelphi, Maryland
Location of Adelphi, Maryland
Country  United States
State  Maryland
County Prince George's
 • Total 2.72 sq mi (7.04 km2)
 • Land 2.72 sq mi (7.03 km2)
 • Water 0.00 sq mi (0.01 km2)
171 ft (52 m)
 • Total 16,823
 • Density 6,194.04/sq mi (2,391.72/km2)
Time zone UTC−5 (Eastern (EST))
 • Summer (DST) UTC−4 (EDT)
ZIP Codes
20783, 20787
Area codes 301, 240
FIPS code 24-00400
GNIS feature ID 0596997

Adelphi is an unincorporated area and census-designated place in Prince George's County, Maryland, United States. Per the 2020 Census, the population was 16,823. Adelphi includes the following subdivisions; Adelphi, Adelphi Park, Adelphi Hills, Adelphi Terrace, Adelphi Village, Buck Lodge, Chatham, Cool Spring Terrace, Hillandale Forest, Holly Hill Manor, Knollwood, Lewisdale, 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 West Hyattsville 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 Hills, Adelphi Knolls, Buck Lodge, Chatham, Cool Spring Terrace, Heitmuller Estates, Hillandale Forest, Knollwood, Riggs Hill Manor, and White Oak Manor. A community focal point originally developed in the late 1950s is the Adelphi Pool.

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.

Historic sites

The following is a list of historic sites in Adelphi identified by the Maryland-National Capital Park and Planning Commission:

Site name Image Location M-NCPPC Inventory Number Comment
1 Adelphi Mill and Storehouse
Adelphi Mill 1.jpg
8401 and 8402 Riggs Road 65-006
2 Cool Spring Farm (Miller’s House) 2201 Cool Spring Road 65-005
3 Gallant House 3124 Powder Mill Road 61-013


Adelphi is located at 38°59′49″N 76°58′0″W / 38.99694°N 76.96667°W / 38.99694; -76.96667 (38.996860, -76.966755).

According to the United States Census Bureau, the CDP has a total area of 2.7 square miles (7.1 km2), all of it land.

Bordering areas


Historical population
Census Pop.
2010 15,086
2020 16,823 11.5%
U.S. Decennial Census
2010 2020

2020 census

Adelphi CDP, Maryland - Demographic Profile
(NH = Non-Hispanic)
Race / Ethnicity Pop 2010 Pop 2020 % 2010 % 2020
White alone (NH) 1,980 1,571 13.12% 9.34%
Black or African American alone (NH) 5,291 4,953 35.07% 29.44%
Native American or Alaska Native alone (NH) 37 36 0.25% 0.21%
Asian alone (NH) 1,168 1,367 7.74% 8.13%
Pacific Islander alone (NH) 5 6 0.03% 0.04%
Some Other Race alone (NH) 53 91 0.35% 0.54%
Mixed Race/Multi-Racial (NH) 207 336 1.37% 2.00%
Hispanic or Latino (any race) 6,345 8,463 42.06% 50.31%
Total 15,086 16,823 100.00% 100.00%

Note: the US Census treats Hispanic/Latino as an ethnic category. This table excludes Latinos from the racial categories and assigns them to a separate category. Hispanics/Latinos can be of any race.


Adelphi is the home of the University of Maryland Global Campus, and the community is located near the University of Maryland main campus in College Park.

Adelphi is served by the Prince George's County Public Schools system. In 2000, a new elementary school opened in the community dedicated to labor organizer Mary Harris "Mother" Jones.

Elementary schools in Adelphi: A southeastern section is zoned to University Park Elementary School in University Park.

Most residents are zoned to Buck Lodge Middle School in Adelphi and High Point High School in Beltsville. A southeastern section is zoned to Hyattsville Middle School and Northwestern High School in Hyattsville.

Notable people

  • John Fahey— Recorded the first Tacoma Records album at the St. Michaels and All Angels Church
  • Fred Funk - professional golfer.
  • Roy Hibbert - NBA player for the Indiana Pacers
  • Mary Harris Jones (1837-1930) - Labor organizer known as "Mother" Jones
  • Hugh V. Perkins (1918-1988) - educator, author, and professor of Education, University of Maryland - College Park.

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