What was the name of the 200th-anniversary milestone that preceded America250?

The 200th-anniversary milestone that preceded America250 was the Bicentennial.

The United States Bicentennial took place in 1976, two centuries after the Declaration of Independence was adopted in 1776. The word “bicentennial” means a 200-year anniversary, from the Latin prefix “bi-,” meaning two, and “centennial,” meaning a period of 100 years.

The bicentennial was a broad national observance rather than one single ceremony. Communities organized parades, exhibitions, cultural programs, historical projects, and public celebrations. The period also included the international Operation Sail gathering of tall ships.

America250 uses a different term because 250 years is not a bicentennial. “Semiquincentennial” is the formal label for 250 years, while “tricentennial” will describe the 300th anniversary in 2076.