In 1917, the department prepared the Marked Through Routes Map. This map displayed major ways and trails with unique signing conventions. In the 1920s, Illinois issued various State Bond Issue maps.

The department prepared the first Illinois Official Highway Map (OHM) in 1932. Its format is similar to the current OHM. The OHM was printed annually through 1972 except in 1943 due to World War II. In 1973 the department issued a 1973-74 map with a biennial printing ever since. The 1991-92 and subsequent OHMs have been prepared digitally.

The OHM is the state’s most popular map and the most familiar to the traveling public. The enlarged version is a fixture in state government offices and educational institutions. Over three million copies of the 1999-2000 OHM were printed for distribution by the department and the Secretary of State.

In 1999, the department printed "The Large Print Edition" of the Illinois Highway Map in developing mapping products that the traveling public need and request. This map is comprised of the top half of the state shown on one side with the bottom half on the reverse side. The printed map is approximately 38% larger than the regular Illinois OHM. This increase sounds small, but makes the map much easier to read. When folded, the map is the same physical size as the regular map.

The Department annually solicits comments and suggested revisions to the OHM from its district offices, other Illinois State agencies, bordering states, and other public and private entities. The department also receives suggestions from the general public. Upon review, the department carefully incorporates needed changes while minimizing clutter so that the OHM remains legible and useful as a traveling tool. Revision data are compiled and sent to commercial mapping companies for use in updating their maps.