Missouri Secondary State Route M is a east-west highway in Northern Jefferson County. It runs from U.S. Rt. 61/67, near Barnhart, to Missouri State Route 21, near Otto. MO Sec St Rt M passes through the following town in Jefferson County. Antonia MO Sec St Rt M is not multi-plexed in Jefferson County. MO Sec St Rt M intersects the following highways in Jefferson County. U.S. Rt. 61, near Barnhart. U.S. Rt. 67, near Barnhart. Interstate 55, near Barnhart. Missouri State Route 21, near Otto.
