How to research a house in Washington, DC
The District's combined assessment and Recorder of Deeds, the building permit database, the DC History Center and the Washingtoniana collection, Baist's real-estate atlases, Sanborn maps, and the census — a guide to tracing a DC rowhouse.
By The Plot Team · May 26, 2026 · 4 min read
Washington is a planned city — Pierre L'Enfant's diagonals laid over a grid in 1791 — and it documents itself like the federal town it is. A Capitol Hill rowhouse, a Shaw Victorian, a Petworth porch-front, a Georgetown federal: each is unusually traceable, partly because the District is its own city, county, and recording jurisdiction all at once. Here's the path.
Start with the parcel: the District's assessment data
The District of Columbia is a single jurisdiction, so the Office of Tax and Revenue (OTR) is your anchor. DC parcels are identified by square, suffix, and lot (SSL) — a system unique to the District, descended from L'Enfant's plan — and the city's open-data platform (opendata.dc.gov) publishes the assessment and computer-assisted mass appraisal (CAMA) data with the address, the year built, the use code, and characteristics. That open layer is the free, automatable tier and the one Plot reads where DC is covered. The SSL is your key to everything downstream.
A DC specialty: the building permit database
Washington has one of the best free house-dating tools in the country. The DC building permits database — original permits from 1877 to 1949, digitized and indexed by the DC Historic Preservation Office and searchable online — names the owner, the architect, the builder, and the cost and dates construction precisely. For a pre-war DC house this is often better than the assessor's year-built, and it's free. Start here once you have the address; it's the single most rewarding DC-specific source.
Trace ownership: the Recorder of Deeds
Deeds are recorded by the DC Recorder of Deeds (part of OTR), whose online records search lets you look up recorded documents by name and by SSL. As with every recorder outside NYC's ACRIS, it's a search-and-order portal with per-document fees rather than a bulk feed. Pull your chain oldest-first to see who built, who bought, and how the house passed hands.
See the block: Baist and Sanborn
DC is gorgeously mapped. The Baist Real Estate Atlases of Washington (G.W. Baist, multiple editions from the 1880s into the 20th century) print lot lines, owner names, and building materials block by block, and the Library of Congress has digitized them free — for a DC house, the Baist atlas is the prize. Pair it with the Sanborn fire-insurance maps (also free at the LOC), which add building-by-building construction detail across editions.
The DC History Center and Washingtoniana
For local history, two collections stand out. The DC History Center (the Historical Society of Washington) holds photographs, manuscripts, building files, and the famous Washingtoniana map and image collections. The DC Public Library's Washingtoniana division (at the MLK Jr. Memorial Library) holds city directories, the Washington Star photographic morgue (a vast digitized collection), neighborhood vertical files, and the building permit index. Between them you can usually put a face on the block.
Find the people: census and directories
The federal census (public 1850–1950) names everyone in the household with ages, occupations, and birthplaces — telling in a city shaped by government service, the Great Migration, and a long-established free Black community. The Boyd's Washington city directories, many digitized on the Internet Archive and held at Washingtoniana, fill the years between counts. Search newspapers through Chronicling America (Library of Congress), which carries the historical Washington papers free.
Landmark status
DC is densely protected. Check whether your house sits in a DC historic district (the Historic Preservation Office keeps the list — Capitol Hill, Georgetown, Shaw, Mount Pleasant, and many more), is an individually designated DC landmark, or is on the National Register. District nominations are themselves detailed histories, and the HPO's building-permit work means much of the architectural research may already be done.
Let Plot assemble the DC record
Plot resolves a Washington address against the District's parcel data and the broad public record automatically — the year built, the lot, the press, archival imagery — and writes a cited history. For the deed chain and the building permits, Plot points you to the DC Recorder of Deeds and the HPO permit database — the parts the city keeps in its own portals — while it gathers everything else for you.