There are 5 US Post Offices in Benton County serving a total of 58,687 residents equating to 11,737 residents per post office. It's estimated that approximately 93,671 packages are handled across the 5 county post offices annually. Benton County is a county located in the U.S. state of Oregon. As of the 2010 census, the population was 85,579. Its county seat is Corvallis. The county was named after Thomas Hart Benton, a U.S. Senator who advocated American control over the Oregon Country. Benton County is designated as the Corvallis, OR Metropolitan Statistical Area, which is included in the Portland-Vancouver-Salem, OR-WA Combined Statistical Area. It is located in the Willamette Valley."