California had been a territory that Polk had desired ever since the annexation of Texas in 1845, and when war with Mexico broke out, he saw the perfect opportunity to take hold of the land he wanted.

On July 9, 1846, the USS Portsmouth, captained by Commander John B. Montgomery, sailed into San Francisco Bay, with the intent of capturing the town of Yerba Buena.

The Portsmouth landed a distance off the shore, and a group of sailors, soldiers and marines, as well as Montgomery and his staff, disembarked in rowboats for Yerba Buena.

He quickly tore it down, and hoisted the Stars and Stripes in its place, proclaiming that the town of Yerba Buena, and all of the land surrounding it, belonged to the United States.

After Montgomery's speech, the marine band began to play Yankee Doodle, and the USS Portsmouth fired a 21 gun salute, to celebrate the capture of Yerba Buena.