Michigan State Route 99 is a north-south highway in Hillsdale County. It runs from the Michigan/Ohio State Line, near Pioneer, Ohio, and runs to the Hillsdale/Calhoun County Line, near Homer. MI St Rt 99 passes through the following towns in Hillsdale County. Jonesville Litchfield MI St Rt 99 is multi-plexed in Hillsdale County. U.S. Rt. 12, at Jonesville. MI St Rt 99 intersects the following highways in Hillsdale County. Michigan State Route 34, near Jonesville. U.S. Rt. 12, at Jonesville. U.S. Rt. 12, at Jonesville. Michigan State Route 49, at Litchfield.