Adelphi’s post office opened in 1880, and 1 of its places is on the National Register
More historic than 47% of U.S. towns · #98 of 261 in Maryland. What drives it
Most of Adelphi was built recently: 2% of its homes predate 1940 and the median home dates from 1968. 1 place in town is on the National Register, among them a historic district with 170 buildings. Below: maps from 1979 on and the census since 2000.
Founding year: the first Adelphi post office (Blevins & Helbock, CC0).The full story ↓
History grade
What drives Adelphi’s History grade
On its age, its old homes and the National Register, Adelphi is more historic than 47% of U.S. towns, #98 of 261 in Maryland. Its National Register listings hold the grade up; its share of homes from before 1940 pulls it down.
B−
HistoryA character grade: shown, never part of Adelphi’s overall grade.
Few Maryland towns list much on the Register (a typical Maryland town has 0.9 per 10,000 residents, the U.S. 2.4), so Adelphi’s 97.7 sits above most of its state (84% of Maryland towns have fewer) while its 170 historic buildings outnumber those of 92% of U.S. towns.
How sure. Graded on any two of the three inputs instead, the letter would range from C− to B+. The pre-1940 share (±1.2 points) is firm at this size. The founding year is the first post office, not a stated founding date.
Founding year: the first post office (other dates in Quick answers). Homes: Census ACS 2020–24. National Register: National Park Service, May 2026 list; each listing counted once (boundary changes and added documentation belong to their listing), and a historic district counts its contributing buildings. How TownRatings grades history →
What stands out about Adelphi’s past
Read from the archive, the National Register and the record. The page puts what stands out first.
The unincorporated Adelphi community takes its name from the historic Adelphi Mill, established in 1796 along the Northwest Branch of the Anacostia River. It 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 rel…
The Adelphi post office opened in 1880, the earliest record of the town by name (U.S. post office records).
How does Adelphi rank for history?
Adelphi is more historic than 47% of U.S. towns, #98 of 261 in Maryland. The History grade combines the town’s founding era, the share of homes built before 1940 and its National Register listings. It’s a character grade, so it isn’t part of the overall grade. How it works.
What is on the National Register in Adelphi?
One place: the College Heights Estates Historic District (listed 2012).
How old are the homes in Adelphi?
2% of Adelphi’s homes were built before 1940 (Census estimate, ±1.2 points), against a typical 3.3% for a Maryland town; the median home was built in 1968.
Founding dates: Wikidata, Wikipedia, the U.S. post office records of Blevins & Helbock (CC0) and the Census. Homes by year built: Census ACS 2020–24. National Register of Historic Places: National Park Service (list of May 22, 2026). Old photos, postcards and papers: Wikimedia Commons, the Library of Congress and other public archives, credited on each item’s page. Maps: U.S. Geological Survey historical topographic maps (via Esri) and Sanborn fire-insurance maps (Library of Congress). History text and census tables: Wikipedia (CC BY-SA 4.0). Places that used to be: USGS Geographic Names Information System (2021).
From the National Register of Historic Places (1), Wikipedia, U.S. Geological Survey historical maps, U.S. Census counts (via Wikipedia), the US Post Offices dataset (Blevins & Helbock) and the USGS Geographic Names Information System. Archive images are copied here with their credits and licenses, shown on each photo’s page. Refreshed monthly.
