Incidentally, the path length from the WSCR tower site to the South Haven, MI shoreline of Lake Michigan is about 98 miles. WSCR's groundwave field of 2 mV/m in South Haven would be produced for an average Earth conductivity of about 9.5 mS/m along that path.
So the poorer inland conductivity of the state of Michigan in that region isn't having much of an affect on the AM signals that cross Lake Michigan to South Haven, from the Chicago area.