What is the official anniversary term for America's 250th birthday in 2026?

The official anniversary term for America’s 250th birthday in 2026 is semiquincentennial.

The word combines “semi,” meaning half, with “quincentennial,” meaning a 500th anniversary. Half of 500 is 250, so a semiquincentennial is a 250th anniversary. The term is less familiar than bicentennial, which describes a 200th anniversary.

Several alternative names have been suggested for the same milestone. These include sestercentennial, bisesquicentennial, and quarter millennium. In public communications, however, the United States Semiquincentennial and America250 are the most recognizable labels.

The anniversary commemorates the 250th anniversary of the Declaration of Independence’s adoption, not the signing of the United States Constitution. The Constitution dates from 1787, while the Declaration was adopted by Congress in 1776. That distinction explains why the national observance centers on July 4, 2026.