Milwaukee County Highway OO runs north-south in the southwestern portion of the county. This runs from Hales Corners to the Milwaukee/Waukesha County Line.
A guide marker on EB WI St Rt 24. Junction marker on SB U.S. Rt. 45/WI St Rt 100. Junction marker on NB U.S. Rt. 45/WI St Rt 100. A junction marker on SB U.S. Rt. 45/WI St Rt 100. A guide marker on SB U.S. Rt. 45/WI St Rt 100.
