practical to implement. The southern third of the state, which was not covered by glaciers during the Illinoian Stage and therefore retains an unglaciated landscape similar to central Kentucky, is too hilly for this. Gridding is also difficult or impossible in counties laid out under other quadrangular mapping systems such as the Vincennes Quadrangular, an older style of mapping system using a river for reference. This is the case in parts of Clark, Gibson, Knox, and Vanderburgh Counties. A similar system is used in parts of White County, where some roads around Lake Shafer indicate mileage from Norway Dam, which itself lies at mile 30.2 of the Tippecanoe River. For example, the road called 4.3 lies 4.3 miles from the dam. See also List of State Roads in Indiana List of state highways in the United States Indiana Toll Road St. Joseph Valley Parkway References External links Indiana Department of Transportation Indiana State Highway Endpoints Indiana Highway Ends Gallery Numbered