The department initiated the County General Highway Map series in 1936. County maps display section lines, city boundaries, waterways and other items at a scale approximating 1:63,360 (1" = 1 mile). The department also issues a 1/2 scale version (1" = 2 miles) of the county map. The format of county maps has remained practically the same since initiation except for changes in accuracy and general appearance. Township and vicinity maps delineate further detail of congested areas.

Initially, the department traced the section line grid of the first county maps from blueprints with no defined horizontal control. Later, cartographers drafted maps from a five minute latitude and longitude grid prepared on polyconic projection. Survey points from United States Geological Survey (USGS) traverse data enabled the plotting of control points. Aerial photographs, linked to these control points, provided the source to draw the roads, section lines and water features on the grid. Cartographers overlaid the grid with drafting lines and used ink to draft the map. Each county map required approximately one year to complete.

In the early 1960s, cartographers prepared the maps with the same control but used stereoscopic viewers and sketchmasters to rectify the aerial photos for road alignment. In the late 1960s, the department added state plane coordinates within the trim line at 25,000 foot intervals.

Initially cartographers prepared maps on coated linen. They used Wrico and then Leroy lettering devices for inking and a crow’s quill for sketching waterways. Cartography required extreme care since water or perspiration would smear the ink, which took a long time to dry.

In the early 1960s, the department replaced linen with mylar. Cartographers developed a stick-up process for all symbols. Text was prepared on sheets and cut and laid over centerlines for the features. This is the process now used to produce the maps along with some scribing.

In the 1930s, maps were shipped to Chicago to produce negatives and prints. In the early 1940s, the Department acquired blueprint machines to print positives. In 1956, the department established a photo lab with equipment large enough to prepare map negatives and positives. This allowed all county maps to be printed internally. In the 1960s, the blueprint process of printing was replaced with the ammonia-based diazo process. In 1993, the department acquired laser printers for map reproduction for convenience and to eliminate the use of ammonia.

Originally, the County General Highway Map Series portrayed all cultural features including buildings, houses and businesses. In the 1980s, the department removed most of these features due to the difficulty of keeping these items current and to reduce clutter.

The County Map Series is a popular product due to its detail, geometric accuracy, and size. It has proven a valuable resource for many local agency and private mapping applications and state agency activities. These maps also provided the base for the department’s Geographic Information System (GIS) efforts.