A little San Francisco naval science:

31 July 1846 – Population of Yerba Buena, Alta California doubled on arrival of the Brooklyn and 240 Mormon migrants.
30 January 1847 – Yerba Buena officially renamed San Francisco.
24 January 1848 – Gold discovered at Sutter's Mill, Coloma, California.

California entered the Union not so much as a “Free” state but an anti-slavery one. It was practiced as a crime, not an institution. That said, the place was in no way welcoming to free African-American migrants.

About half the 300.000 migrants came overland. The others either via Panama or around the Horn. No barges either way.

With the exception of the bar at the mouth of the Sacramento River, it was steamboat draft all the inland way to Sacramento.

On paper, the United States had just taken the port from Mexico. In practice in was a South American managed facility. USN Lt. W.A. Bartlett, the first U.S. citizen Alcalde, was chosen partly for his fluency in Spanish. The various waterfronts that replaced the earlier lighter scows and barges are still called embarcadero today.