What is the formal name of America's 250th anniversary celebration, also called America250?

The formal name of America's 250th anniversary celebration is the United States Semiquincentennial.

“Semiquincentennial” combines semi-, meaning half, with quincentennial, meaning a 500th anniversary. Together, the word describes 250 years, or half of five centuries. America250 is the branding used for the nationwide commemoration.

The celebration marks the 250th anniversary of the United States Declaration of Independence, adopted in 1776. Official planning began with the congressional, nonpartisan United States Semiquincentennial Commission, established in 2016.

The event is sometimes also called the Bisesquicentennial, Sestercentennial, or Quarter Millennium. These alternatives are less common than “Semiquincentennial,” which is the name used in the commission’s title and major reference materials.