What is the formal name for the United States’ 250th-anniversary observance called America250?

The formal name for the United States’ 250th-anniversary observance called America250 is the United States Semiquincentennial.

“Semiquincentennial” combines terms meaning half of five hundred years. It describes the 250th anniversary of the United States Declaration of Independence, adopted on July 4, 1776. America250 is the shorter public-facing name used for the commemoration.

The anniversary has several less common alternative names, including sestercentennial, quarter millennium, and bisesquicentennial. Semiquincentennial is the term used in the title of the principal Wikipedia article and in many formal descriptions of the national observance.

The word can be confused with “bicentennial,” which means a 200th anniversary. The United States celebrated its Bicentennial in 1976, exactly two centuries after the Declaration of Independence. The 2026 observance marks a further half-century milestone.