Fond du Lac, WI, was a very busy rail hub with Milwaukee Road running to the southwest to Horicon, Soo Line to the southwest to Waukesha and northwest to Stevens Point, plus Chicago North Western had lines from Sheboygan to the east, Milwaukee to the southeast, Janesville to the southwest, Wisconsin Rapids to the west-northwest and Green Bay to the north. All of this in addition to very busy rail yards for both CNW and Soo Line. The yards are still pretty busy as are the repair facilities but the only lines that are still active are the former Soo Line to the southwest and the CNW north.
The Chicago North Western line from Fond du Lac to Clyman Junction to the south was still active in the late 1970s but was abandoned and the tracks removed in the early 1980s. The Wild Goose rail-trail now runs along the abandoned right-of-way; there has been some recent interest on the part of the Wisconsin Southern Railroad to relay some track along this route.
Thanks to Beaver for contributing information about this route.