How to research a house in Seattle
King County parcel data with real year-built, the Recorder's LandmarkWeb deed search, the Seattle Public Library and Puget Sound Regional Archives, Sanborn maps, and the census — how to trace a Seattle house from a Ballard bungalow to a Capitol Hill foursquare.
By The Plot Team · May 30, 2026 · 4 min read
Seattle's housing grew up with the city — the Klondike money of the 1890s, the Boeing booms, the regrades that literally flattened the hills — and the records track that growth closely. A Ballard bungalow, a Capitol Hill foursquare, a Wallingford box, a Central District Victorian: all are traceable. Here's the path through King County.
Start with the parcel: King County assessor data
Your anchor is the King County Assessor. The county publishes parcel and assessment data — keyed to a parcel number (PIN) — that carries the situs address, the year built, the building grade and type, and the number of units. The Assessor's eReal Property lookup shows it per address, and King County's open GIS layers carry it in bulk; this is the free, automatable tier, and it's the parcel data Plot reads where King County is covered. Note the year built the same way you'd treat any assessor's figure: a strong hint, occasionally rounded for older stock.
Trace ownership: the King County Recorder
Deeds in Seattle are recorded by the King County Recorder's Office, whose document search runs on Cott Systems' LandmarkWeb. Be precise about what's free here: the online index and images are free for documents recorded on or after August 1, 1991. For anything older — which is most of a pre-war house's chain — you're ordering copies or visiting in person, and the system is a session-based search, not a bulk feed. Search by PIN or by grantor/grantee name, oldest-first, to see who built, who bought, and how the house changed hands.
See the block: Sanborn maps
The Sanborn fire-insurance maps cover Seattle in detail and are free through the Library of Congress. They show your block footprint by footprint, color-coded by construction material, across editions from the 1880s into the mid-20th century — invaluable for dating construction and watching a platted addition fill in with houses. The University of Washington Libraries hold additional Sanborn sheets and an outstanding regional map collection.
Find the people: census and directories
The federal census (public 1850–1950 under the 72-year rule) names everyone in the household with ages, occupations, and birthplaces — telling in a city built by Scandinavian, Japanese, Filipino, and later Black migration. Search by address or surname through the National Archives, FamilySearch, or the 1950 census site. Between censuses, the Polk Seattle city directories, many digitized on the Internet Archive and held at the Seattle Public Library, list residents year by year and help you track when a family moved in or out.
The Seattle Public Library and the regional archives
The Seattle Public Library's Seattle Room is a deep local-history collection — directories, photographs, neighborhood files, and the Seattle Times historical index. For original records, the Puget Sound Regional Branch of the Washington State Archives (on the Bellevue College campus) holds King County's historical records: plats, early permits, and assessment rolls. The Museum of History & Industry (MOHAI) and the UW's digital photo collections are superb for street-level imagery.
A Seattle specialty: the regrades and the plats
Two things make Seattle house history distinctive. First, the regrades — between roughly 1898 and 1930 the city sluiced away Denny Hill and reshaped much of downtown and its edges. If your parcel sits in a regrade district, its usable history often begins with the regrade, the earlier ground (and any building on it) literally washed into Elliott Bay. Second, like most western cities Seattle was built plat by plat: a recorded subdivision map carved a tract into numbered lots and blocks, and your deed's legal description names that plat and lot. Follow the plat name — "Gilman's Addition," "Boren's," "Sarah A. Bell's" — and you'll usually pin the year your street was laid out, and the platting often survives as the neighborhood's name.
Landmark status
Check whether your house is a designated Seattle Landmark (the city's Landmarks Preservation Board publishes designation reports, themselves mini-histories), sits in one of the city's historic districts (Pioneer Square, Ballard Avenue, Columbia City, Harvard-Belmont, and others), or is on the National Register. A designation report often hands you the architectural and ownership work already done.
Let Plot assemble the Seattle record
Plot resolves a Seattle address against King County's parcel data and the broad public record automatically — the year built, the lot, the Chronicling America press mentions, archival imagery — and writes it up as one cited history. For the deed chain, Plot points you straight to the King County Recorder's LandmarkWeb search (free index back to 1991, copies and the archive for the rest), so you can pull the documents the county doesn't expose in bulk while Plot handles everything around them.