What is the formal historical name for the anniversary celebrated by America250?

The formal historical name for the anniversary celebrated by America250 is the United States Semiquincentennial. It describes the 250th anniversary of the Declaration of Independence and the founding of the United States.

The term is built from Latin-derived number roots: “semi” means half, “quin” relates to five, and “centennial” refers to a hundred-year period. In practical terms, a semiquincentennial is half of five centuries, or 250 years.

Other names have appeared in historical and popular usage, including “sestercentennial,” “bisesquicentennial,” and “quarter millennium.” America250 is the more accessible public-facing name for the federal commemoration, while “United States Semiquincentennial” identifies the anniversary itself.