Use the National Map to view selected data layers from the U.S. Geological Survey, U.S. Forest Service, U.S. Fish and Wildlife Service, the Bureau of Land Management, and more. The National Map is a collaborative project to provide current data and maps to the public. Data and maps can be viewed with merely a web browser, printed, or downloaded for use with GIS software. This is a great source for topographic maps (or data layers) and Digital Orthophoto Quadrangles.

Land remote-sending data from USGS (Earth Resources Observation and Science (EROS) Center). Search and browse the collections of aerial and satellite imagery, elevation data, land cover, digital line graphs (DLG) and digital raster graphics (DRG). This massive archive includes 70 years of national data and 50 years of global data.

The U. S. Census is a major source of data used for mapping with GIS. The page linked here gives an overview of the resources provided by the census, along with links, such as TIGER, LandView, Census Tract Resources, and reference resources.

This page provides links to the various ways you can access topographic maps from the USGS.

Several articles to provide background and guidance on using topographic maps.

Part of the Geospatial One-Stop E-Gov initiative, this web site allows one to search or browse data categories of geospatial information. The GeoData Map Viewer allows you to view multiple Internet map services (like the National Map) using just your browser. Map servers viewable include the USGS, FEMA Hazard Maps, NASA Globe program, NOAA, and the BLM. State and regional servers are being added, including the Minnesota Metro GIS Data Finder.

This page provides links and information for acquiring topographic maps, digital raster graphics (DRG), thematic maps, and planetary maps and images.