An inset map is a smaller map featured on the same page as the main map. Traditionally, inset maps are shown at a larger scale (smaller area) than the main map . Often, an inset map is used as a locator map that shows the area of the main map in a broader, more familiar geographical frame of reference. Inset maps may also be used to show the detail of a particular area of interest on a map.
Inset maps are used by cartographers to highlight information that would be difficult to perceive at the scale of the main map. This highlighted information may include symbols or points of interest that add to the purpose of the map and address its audience. This technique should be done for a highlighted area of significance, as the viewer will attach greater importance to the inset map.
An effective inset map follows the same design principles as any map, even though it is featured in a smaller frame. The inset should be placed away from the visual center of the map but in a balanced location where the viewer will be able to clearly see it and recognize that it is not an extension of the main map . The most common way this distinction is made is through a border around the area of interest on the main map or through a text explanation on the insert map itself. A good inset should use similar colors and text as the main map to give them a feeling of unity. The scale should be clearly indicated on the inset map if it is not the same as the main map . If the inset map is not North oriented, an indication such as a north arrow or graticule should be used. 
There are several kinds of inset maps that each serve a very different purpose:
- Non-Contiguous Area: Show areas that are not geographically contiguous to the main area of the map. A common example of this kind of inset map is the inset maps of Hawaii and Alaska on maps of the United States 
- Context: The inset map is at a significantly smaller scale than the main map, showing where the main map is in relation to a larger region.
- Detail: The inset map is at a significantly larger scale than the main map, zooming in on an area that has greater detail that is not clear on the main map.
- Thematic: The inset map covers the same or similar area as the main map, with a different topic. Typically the inset map topic is related to, or supportive of, the topic of the main map.
Uses of Inset Maps
There could be many reasons to have an inset map, some of these reasons might include:
- Focusing on a particular area at a larger scale in greater detail.
- Showing the location of the main map in a much broader geographic context.
- Showing different information of the same area as the main map (or other inset maps) to facilitate direct comparisons.
- Showing the same information for a related location that cannot easily fit into the same map (e.g. insets of Alaska and Hawaii on maps of the United States).
- (2006). Maps tutorial: The elements of a map, Maps and Cartography. Geospatial Resources and Map Collection, Ball State University Libraries. Retrieved 2 Oct 2011.
- Buckley, A. (2008). Cartographic design: Inset Maps, Esri Mapping Center. Retrieved 2 Oct 2011.
- Robinson, Morrison, Muehrcke, Kimberling, Guptil. Elements of Cartography, Sixth Edition, Wiley & Sons, p. 337. ISBN 0471555797
- Buckley, Aileen. "Cartographic design: Inset maps." Blog. ArcGIS Blog. Esri, 4 March 2008. Web
- Tyner, J. A. Principles of map design. New York, NY: The Guilford Press, 2010.Print.
- Tyner, p. 38