There are 15 US Post Offices in Ottawa County serving a total of 180,491 residents equating to 12,033 residents per post office. It's estimated that approximately 288,084 packages are handled across the 15 county post offices annually. Ottawa County is a county located in the U.S. state of Michigan. As of the 2010 census, the population was 263,801. The county seat is Grand Haven. The county is named for the Ottawa Nation. It was set off in 1831 and organized in 1837. Ottawa County is included in the Grand Rapids-Wyoming, MI Metropolitan Statistical Area."