There are 16 US Post Offices in Cameron County serving a total of 348,333 residents equating to 21,771 residents per post office. It's estimated that approximately 555,978 packages are handled across the 16 county post offices annually. Cameron County, officially the County of Cameron, is the southernmost county in the U.S. state of Texas. As of the 2010 census, its population was 406,220. Its county seat is Brownsville. The county was founded in 1848 and is named for Captain Ewen Cameron, a soldier during the Texas Revolution and in the ill-fated Mier Expedition. Cameron County is part of the Brownsville\u2013Harlingen, TX Metropolitan Statistical Area as well as the Brownsville\u2013Harlingen\u2013Raymondville, TX Combined Statistical Area.