SS California was one of the first steamships to steam in the Pacific Ocean and the first steamship to travel from Central America to North America. She was built for the Pacific Mail Steamship Company which was founded April 18, 1848 as a joint stock company in the State of New York by a group of New York City merchants: William H. Aspinwall, Edwin Bartlett, Henry Chauncey, Mr. Alsop, G.G. Howland and S.S. Howland. She was the first of three steamboats specified in a government mail contract to provide mail, passenger, and freight service from Panama to and from San Francisco and Oregon.

A steamboat is a boat that is propelled primarily by steam power, typically driving propellers or paddlewheels. Steamboats sometimes use the prefix designation SS, S.S. or S/S (for 'Screw Steamer') or PS (for 'Paddle Steamer'); however, these designations are most often used for steamships.

The term steamboat is used to refer to smaller, insular, steam-powered boats working on lakes and rivers, particularly riverboats. As using steam became more reliable, steam power became applied to larger, ocean-going vessels.