Plainfield’s post office opened in 1819, and 41% of its homes were built before 1940
Its Register listing is the Thomas Johnson House.
How Plainfield began
When was Plainfield founded?
The Plainfield post office opened in 1819, the earliest record of the town by name.
1 historic place in Plainfield
The country’s official list of buildings and places worth saving.
Architectural styles listings
National Park Service, National Register of Historic Places. Photos from Wikimedia Commons, credited on each place’s page.
Questions about Plainfield’s history
What year was Plainfield founded?
The Plainfield post office opened in 1819, the earliest record of the town by name (U.S. post office records).
What is on the National Register in Plainfield?
One place: the Thomas Johnson House (listed 1982).
Memory lane
What the archives can’t tell you, neighbors can.
Where this page comes from
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). How TownRatings grades history →
From the National Register of Historic Places (1), 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.