Missouri Secondary State Route YY is a short north-south highway in Callaway County. It runs from Interstate 70/U.S. Rt. 40/Missouri Secondary State Route D to the Callaway/Montgomery County Line. MO Sec St Rt YY does not pass through any towns in Callawway County. MO Sec St Rt YY is not multi-plexed in Callaway County. MO Sec St Rt YY intersects the following highways in Callaway County. Interstate 70, near Williamsburg. U.S. Rt. 40, near Williamsburg. Missouri Secondary State Route D, near Williamsburg.