USGS national and regional geologic and hydrologic maps in series are in grey file cabinets in Kresge Library, and are shelved by series letter and number. Extraterrestrial geologic maps are there also.

The book, Guide to USGS Geologic and Hydrologic Maps, is a guide to these maps, and to maps in the USGS Bulletins and Professional Papers. It allows you to locate maps by quadrangle name, county and state, coordinates, or type of map. The Guide is located above the map cases in Kresge.

• Many geological maps are published as part of journal articles and books, and can be found attached to those publications in Kresge Library.
• Most of the flat maps in the library collections are shelved in the Evans Map Room on the 2nd floor of Berry Library, which also has a variety of indexes for locating particular maps.
• The Library Catalog contains records for many of the individual maps in the library system - search by subject (example) or by keyword (example).

Good sources of maps on the Web are:

• The Perry-Castañeda Library Map Collection is a general collection of more than 250,000 maps covering all areas of the world, and includes historical and thematic maps. More than 5,000 map images are available online.
• USGS Store helps you identify maps, and locate a source for ordering them.
• USGS Geography section mapping activities and products
• The National Atlas of the United States project includes maps ranging from an interactive map of potentially active volcanoes in the U.S. to shaded relief maps to land cover maps based on remotely sensed data
• Microsoft's TerraServer has USGS Digital Raster Graphics (DRGs), which present coverage of the conterminous United States in 1:24,000-, 1:25,000-, 1:100,000-, and 1:250,000-scale maps.
• Geographic Names Information System (GNIS) is a useful reference for locating information about geographic places and features. It provides coordinates and location information, plus links to some maps that include the feature.
• National Geospatial-Intelligence Agency GEOnet Names Server This searchable gazetteer of worldwide geographic names and coordinates has output to GIS options.
• Omni Resources Catalog A catalog of international print and digital maps and atlases.
• The David Rumsey collection of historical maps is useful for comparative studies of changes over time.