Complex sentence: Probably due to his familiarity with the west coast, in 1848 Bartlett was assigned to the Pacific coast survey on January 9,1849 left for San Francisco in command of the USS Ewing.
Split into simpler sentences: Probably due to his familiarity with the west coast, in 1848 Bartlett was assigned to the Pacific coast survey. On January 9,1849, he left for San Francisco in command of the USS Ewing.