There are 7 US Post Offices in Jefferson County serving a total of 30,304 residents equating to 4,329 residents per post office. It's estimated that approximately 48,369 packages are handled across the 7 county post offices annually. Jefferson County is a county located in the U.S. state of Washington. As of the 2010 census, the population was 29,872. The county seat and only incorporated city is Port Townsend. The county is named for Thomas Jefferson. Jefferson County was formed out of Thurston County on December 22, 1852, by the legislature of Oregon Territory, and included the northern 4,854 square miles (12,571.8 km2) portion of the Olympic Peninsula. On April 26, 1854, the legislature of Washington Territory created Clallam County from the northwestern 2,670 square miles (6,915.3 km2) portion of this original area. The Hood Canal Bridge connects Jefferson County to Kitsap County, Washington. The Coupeville-Port Townsend route of the Washington State Ferries connects the county to Whidbey Island in Island County, Washington.