In the United States Semiquincentennial celebrated by America250, “semiquincentennial” marks 250 years.
The term combines “semi,” meaning half, with “quincentennial,” meaning a 500th anniversary. Half of 500 is 250, so a semiquincentennial is a 250th anniversary. America250 uses the term for the national commemoration of the United States’ 250th anniversary in 2026.
The date connects to July 4, 1776, when the Continental Congress adopted the Declaration of Independence. The 250th anniversary therefore falls on July 4, 2026. The commemoration is also described as the United States’ semiquincentennial or 250th anniversary of independence.
The name can be confused with better-known anniversary terms. A centennial marks 100 years, a bicentennial marks 200 years, and a tricentennial marks 300 years. The 1976 celebration was the United States Bicentennial, while the 1876 Centennial Exposition marked the nation’s 100th anniversary.