The town was originally known as "Trecothick", after Barlow Trecothick, a Bostonian who moved to London. He was an alderman, a Member of Parliament (MP), and a Lord Mayor of the City of London. He had a country estate at Addington, London, now called Addington Palace.
The name of the town was changed to "Ellsworth" in 1802, in honor of Chief Justice Oliver Ellsworth.
The first census of the town, in 1800, reported 47 residents.
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 Wikimedia Commons (2), 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.