There are 24 US Post Offices in Multnomah County serving a total of 521,562 residents equating to 21,732 residents per post office. It's estimated that approximately 832,471 packages are handled across the 24 county post offices annually. Multnomah County /m\u0259lt\u02c8no\u028am\u0259/ is one of 36 counties in the U.S. state of Oregon. As of the 2010 census, the county's population was 735,334, making it the most populous county in Oregon. Its county seat, Portland, is the state's largest city. Multnomah County is part of the Portland-Vancouver-Hillsboro, OR-WA Metropolitan Statistical Area, and though smallest in area, it is the state's most populous county.