The Monument and grave of 517 unknown soldiers of the Spanish, Mexican and U.S. Armies serves as a history lesson.

The Presidio of San Francisco was established by Spain in 1776, the year the U.S. declared its independence from the British Empire.  Mexico gained its independence from Spain in 1821 and took over the Presidio.

Two decades later, the U.S. and Mexico were fighting a territorial war.  With the land North of the Rio Grande and from Texas to California in U.S. hands, the war ended in 1848 and the U.S. took control of the Presidio of San Francisco.  A City Birds digital photo.