Maps and charts often use stylized shapes and symbols as well as common map colors to designate certain features (such as mountains, highways, or cities). The map legend is a small box or table on the image that explains what those symbols means. The legend may also include a map scale for helping to determine distances.
Designing a Key LegendIf you are designing a map you may come up with your own symbols and colors or you may rely on standard sets of icons, depending on the purpose of your illustration. Legends generally appear near the bottom of a map or around the outer edges. They may be placed outside or within the map. If placing the legend within the map, make sure to set it apart with a definite frame or border and don't cover up any important portions of the map. While it can vary, the typical legend has a column with the symbol followed with a column describing what that symbol represents (the label).
Some help with legends:
How to Create a Map Legend
A simple eHow tutorial describes steps to creating the key to your map.
"The legend should be on your map for easy reference, and it should include all of the symbols that you have used for your map. It is important to consider if your map is going to be in color or in black and white, because that will affect the types of symbols that you choose."
Tips for Legend Design
This ArcGIS Resources article has three useful design tips for your map legend including when and when not to label your legend as a legend.
"Design your map symbols to be self evident. In most cases, it is desirable to find yourself in a position of being able to eliminate a legend altogether."
Map Design (PDF)
Before you create the legend you need the map. This article describes the most common elements of a map (including the legend) and discusses balance, contrast, visual hierarchy and other design considerations for creating a map. From Northern Arizona University Geography, Planning, and Recreation.
"Map Legend: The principal symbol-referent description on the map; subordinate to the title, but a key element in map reading; serves to describe all unknown or unique symbols used."
Map Reading (Map Parts)
From About.com Geography, map reading basics beginning with the legend.
"...map symbols used in the United States are often used for different things in other countries. The symbol for a secondary highway on a USGS Topographic map is equivalent to a railroad in Switzerland. Make sure to read the legend and you'll understand the symbols."
Symbols for Use in Maps and LegendsBrowse a variety of map symbols.
Cartographic Symbols & Map Symbols Library
Browse a collection of symbols, get samples, or purchase symbols in Mac/Windows Illustrator format.
Multiple resources that illustrate and discuss a wide range of common map symbols. At Symbols.net
Microsoft: Map Symbols
View and purchase a font full of symbols.
Topographic Map Symbols (PDF)
From the U.S. Geological Survey (USGS), read about topographic maps and see a chart of symbols.
Urban Fonts has some symbol fonts for download. Some of them are symbols you might use on a map.
Also Known As: legend | key legend | map key | key