The map of the 1854 Broad Street cholera outbreak clearly shows how the epidemic spread from residents drinking contaminated water. John Snow’s study showed how the contaminated water supply was linked to the maximum fatalities in close proximity to a specific water pump. These fatalities were represented by points on the map. The most points surrounded the contaminated water supply. Thus a map was able to prove what John Snow suspected as the cause of the outbreak.
The map below of Alaska contains a number of layers showing the regions, airports, lakes and many other features of interest.
In most cases the final map, for printed output, will contain a legend to explain what the various points, lines and polygons represent.