A mental map shows a visual image inside a person's head; these images are very abstract but represent an actual location; it may be of places a person has traveled and the details that the person knows about the various locations. In this particular map, it seems that it is portraying places that a person visited along with various events that took place at each location around Coal City, Illinios in the 1940s.
This map was taken from http://www.uky.edu/~ulack/Geo152/unnumbered%20figure%20pg%2003.jpg.
