San Ygnacio’s post office opened in 1876, and 29% of its homes were built before 1940
3 places in town are on the National Register, among them the Trevino-Uribe Rancho, a National Historic Landmark, and a historic district with 36 buildings.
How San Ygnacio began
When was San Ygnacio founded?
The San Ygnacio post office opened in 1876, the earliest record of the town by name.
3 listings protect 39 historic buildings
The country’s official list of buildings and places worth saving. One is a National Historic Landmark, the highest tier.
Architectural styles listings
★ LandmarkAll 3 listings
National Park Service, National Register of Historic Places. Photos from Wikimedia Commons, credited on each place’s page.
Old corners and burying grounds
San Ygnacio’s post office has been open since 1876.
US Post Offices dataset (Blevins & Helbock, CC0). Places and cemeteries from the USGS Geographic Names Information System (2021).
Questions about San Ygnacio’s history
What year was San Ygnacio founded?
The San Ygnacio post office opened in 1876, the earliest record of the town by name (U.S. post office records).
What is on the National Register in San Ygnacio?
Three places: the Trevino-Uribe Rancho (listed 1973), the San Ygnacio Historic District (1973) and the San Francisco Ranch (1977).
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 (3), 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.