The United States of America declares War on Spain, April 25th, 1898.

The United States of America declared War on Spain, on April 25th, 1898, in response to Spain's declaration of War, on April 23rd. The United States considered the begining of the conflict to have been April 21st, 1898. (The April 21st date is known as "Muster Day" and is one of the Commerative Day's in The Sons of Spanish-American War Veterans, along with April 25th).