In the 1960s, the old Will County Courthouse was torn down and with the construction of the new courthouse and parking lot on the east side of the building, Chicago Street soon was no longer accommodate through traffic. Route 66 was again rerouted in Joliet. The mother road moved to Scott Street, and became a one-way north route, as Ottawa Street continued to act as Route 66 to the south.

At the same time, other major changes to the road also took place. Traffic in downtown Joliet became congested that Route 66 was moved outside of Joliet and diverted around it to pass through Plainfield. In an effort to avoid confusion, the new route through Joliet was named Route 66A and the bypass alignment was then known as regular Route 66. The road traveled down what are now the north side frontage roads of I-55 to Route 126 to Route 59.