There are 16 US Post Offices in Sanilac County serving a total of 42,174 residents equating to 2,636 residents per post office. It's estimated that approximately 67,314 packages are handled across the 16 county post offices annually. Sanilac County is a county located in the U.S. state of Michigan. As of the 2010 census, the population was 43,114. The county seat is Sandusky. The county, which is part of the Thumb region, was created on September 10, 1822, and was fully organized in 1848. Sanilac County is considered to be part of the Thumb of Michigan, which in turn is a subregion of the Flint/Tri-Cities. Sanilac County enjoys seasonable tourism in towns such as Lexington, Port Sanilac, and Carsonville. Sanilac County is economically attached to St. Clair County and Huron County and has very fertile, flat land."