What term describes the 250th anniversary that America250 celebrates?

The term for the 250th anniversary celebrated by America250 is semiquincentennial.

A semiquincentennial is an anniversary marking 250 years. The word combines “semi-,” meaning half, with “quincentennial,” a 500th anniversary. The term is less familiar than “centennial,” for 100 years, or “bicentennial,” for 200 years.

The United States Semiquincentennial refers specifically to the national observance connected with American independence in 1776. America250 is the shorter public-facing name used for the celebration and its programs.

The term can be confused with “sesquicentennial,” which means a 150th anniversary. “Quincentennial” alone means 500 years, so it does not describe the 2026 milestone. The unusual vocabulary is one reason the celebration is frequently identified by the simpler America250 name instead.