Rush Lake (Wisconsin)Rush Lake is a lake located in Winnebago County and Fond du Lac County, Wisconsin.Size and ShapeRush Lake is roughly shaped like an inverted triangle; the lake is widest at its north end. It covers an area of, and reaches a maximum depth of. The lake is rather shallow, with an average depth of only.LocationRush Lake is mainly located in Winnebago County, about southwest of Oshkosh. Only the southern most point is in Fond du Lac County near Wilmoore Heights.