U.S. Federal Route 77 is a north-south highway running in Central Carter County. This is a surface alternate to Interstate 35. U.S. Rt. 77 passes through the following towns in Carter County. Ardmore Springer U.S. Rt. 77 is not multi-plexed in Carter County. U.S. Rt. 77 intersects the following highways in Carter County. Oklahoma State Route 77S, near Lake Murray. U.S. Rt. 70, at Ardmore. Oklahoma State Route 199, at Ardmore.