The completion of Interstate 29 in South Dakota , which generally followed US 77 northward , meant the end of the U.S. Highway 's importance .
Within a couple years , US 77 would be truncated to the I - 29 interchange .
The completion of I - 29   in South Dakota , which generally followed US 77 northward , meant the end of the U.S. Highway 's importance .
Within a couple years , US 77 would be truncated to the I - 29 interchange .