The flag of Mexico was first introduced in 1821 as a basic green, white, and red tricolor. In 1823 the Mexican coat of arms, which represents the 1325 founding of the Aztec capital Tenochtitlán (on the site occupied by the country's modern capital, Mexico City), was added in the center white stripe. The coat of arms has changed several times since, which has been reflected in modifications to the flag.