It ran north–south in south central Wisconsin from the entrance to Devil's Lake State Park to Baraboo.

It was phased out in June 2016 and turned over to local jurisdictions and County DL was extended.

Starting at the entrance of Devil's Lake State Park, WIS 123 briefly traveled northeastward.

It continued to travel northward towards downtown Baraboo via present-day CTH-DL, Walnut Street, and Parkway.

After crossing above the Baraboo River, they began to run concurrently with WIS 113.