Content is contained in the legend to aid in the interpretation of the map.

It is able to fulfill its purpose of informing what the different colors mean, but it is higher on the visual hierarchy that the actual geographic area being looked at. The legend, however, is very large and can be very distracting. The legend is key here in order to understand the data that is being presented on the choropleth map. It should be large enough that it is legible but small enough to stay low in the visual hierarchy. The legend should be simple and its position largely depends on the open space available in the map a legend should be centered in an area of open space. Creating a well laid out legend will enhance the overall gestalt of the maps visual appearance. Therefore, it is important to remember the layout design concepts such as harmony, visual balance, clarity, visual logic, logical groupings, and unambiguous references to create a legend that is effective in relation to the map. The only difference is that it is related to the information on the map it is connected to. The legend is a graphical representation of information, with design principles similar to a map or any other graphic. Because map symbols’ meanings vary from region to region, a clear and concise legend is critical for conveying the distinctive characteristics of the map.

For example, a short segment of a blue sinuous line may be labeled 'rivers'. It typically includes a sample of each symbol (point, line, or area), and a short description of what the symbol means.

A map legend or key is a visual explanation of the symbols used on the map.

Legend definition