Illuminated contour lines, where line width and color are varied based on an angle of illumination, date back to the mid-nineteenth century, but their effectiveness compared to conventional contour lines has not been fully examined. Currently, illuminated contour lines are not widely used in computer-based cartography because they are not included in most GIS and mapmaking software. This article introduces improvements to existing algorithms for creating illuminated and shadowed contour lines from digital elevation data. A software package is made available to allow mapmakers to more easily make customized illuminated contour maps. A user study comparing illuminated contour lines to other relief representation techniques with 400 participants was conducted. The results indicate that map-readers can interpret relative height differences between points better and quicker with illuminated contour lines than regular contour lines or shaded relief. Study participants were able to select absolute maxima on an unlabeled illuminated contour map and a labeled regular contour map with equal accuracy and timing. These findings suggest that illuminated contour lines could be used more frequently for improved visualization of terrain and other surface data on maps.