Pacific County is a county located in the U.S. state of Washington. As of the 2010 census, the population was 20,920. Its county seat is South Bend, and its largest city is Raymond. The county was formed by the government of Oregon Territory on February 4, 1851 and is named for the Pacific Ocean.The unincorporated community of Oysterville, established in 1852, was the original county seat until the late 19th century when it changed to South Bend.