There are 9 US Post Offices in Linn County serving a total of 13,865 residents equating to 1,541 residents per post office. It's estimated that approximately 22,130 packages are handled across the 9 county post offices annually. Linn County is a county located in the northern portion of the U.S. state of Missouri. As of the 2010 census, the population was 12,761. Its county seat is Linneus. The county was organized January 1, 1837 and named for U.S. Senator Lewis F. Linn of Missouri.