There are 15 US Post Offices in Monroe County serving a total of 116,394 residents equating to 7,760 residents per post office. It's estimated that approximately 185,778 packages are handled across the 15 county post offices annually. Monroe County is a county located in the U.S. state of Michigan. As of the 2010 census, the population was 152,021. The largest city and county seat is Monroe. The county was established as the second county (after Wayne County) in the Michigan Territory in 1817 and was named for then-President James Monroe. Monroe County comprises the Monroe, MI Metropolitan Statistical Area and is included in the Detroit-Warren-Ann Arbor, MI Combined Statistical Area. It is unofficially considered a northerly extension of the Toledo Metropolitan Area."