Missouri Secondary State Route A is an east-west highway in Southwest Boone County. This runs from U.S. Rt. 63 to the town of Hartsburg. MO Sec St Rt A passes through the following town in Boone County. Hartsburg
MO Sec St Rt A is not multi-plexed in Boone County. MO Sec St Rt A intersects the following highway in Boone County. U.S. Rt. 63, near Ashland.