What is the formal term for America’s 250th anniversary?

The formal term for America’s 250th anniversary is semiquincentennial.

The word combines “semi,” meaning half, with “quincentennial,” meaning a 500th anniversary. A semiquincentennial therefore marks half of 500 years, or 250 years. The 2026 anniversary commemorates the 250th anniversary of the Declaration of Independence’s adoption in 1776.

Several less common names have also appeared in discussions of the anniversary, including sestercentennial, quarter-millennium, and bisesquicentennial. However, “United States Semiquincentennial” is the standard formal name used for the national milestone.

The term should not be confused with bicentennial, which means 200 years. The United States celebrated its bicentennial in 1976, exactly two centuries after the Declaration. Its next major 500-year milestone will be the quincentennial in 2276.