You are standing on what was a shore in 1846 when Captain Montgomery sailed USS Portsmouth here from Sausalito to raise the American flag and claim the few houses that were San Francisco for the United States. Look East - everything you see is built on buried ships and luck.
Portsmouth Square is one of the three roots from which San Francisco grew (the other two being the Mission and the Presidio).
Here the first public school in California was erected in 1847, and here in 1848 Sam Brannan showed everyone the first Californian gold. In 1849 John Hamilton opened California's first book store here.
In 1849 San Franciscans gathered here to demand representation at the Monterey Constitutional Convention and again to form the Vigilance Committee for suppression of the Hounds gang. Here, too, was held the celebration for California's admission into the Union in 1850.
Here the world's first successful cable car line, Clay Street Hill Railroad, opened in 1873 brought about by Andrew Hallidie's desire to decrease the suffering of horses.
Here San Franciscans gathered to mourn the death of Robert Louis Stevenson and to commemorate the Tianmen Square massacre.
The square changed with the city. It is not the same now as it was when Dr. Sun Yat Sen walked here, and the square he saw was not one known to General Vallejo. Perhaps it is this constant change and constant greedy aggregation of memories are what make Portsmouth Square the true heart of San Francisco.