What is the standard name for a 250th anniversary, such as America250?

The standard name for a 250th anniversary, such as America250, is semiquincentennial.

The word combines “semi,” meaning half, with “quincentennial,” relating to 500 years. In practical usage, it identifies the midpoint between a bicentennial, or 200th anniversary, and a tricentennial, or 300th anniversary.

The term is less familiar than bicentennial because national celebrations at 250 years are relatively uncommon. Alternative labels include sestercentennial, quarter-millennium, and bisesquicentennial, but semiquincentennial is the principal name used for the United States’ 2026 observance.

The naming sequence helps place America250 alongside earlier anniversaries. The United States marked its centennial in 1876, sesquicentennial in 1926, and bicentennial in 1976. Each label describes the number of years since the 1776 Declaration of Independence.