The Federal Government used your tax dollars to map, in detail, the entire
United States. This gigantic undertaking was done by the United States
Geological Survey (USGS). Every line on every topo map that the USGS produced was drawn in by hand, there were no computers when this project started. Check out the fascinating history of how topo maps are made here. Maps were
previously printed and sold at cost, usually around three dollars, at any one of the Major Field Offices.
Private companies now own digital copies of the maps. While you can still buy paper copies for around six dollars, digital copies are for sale for a lot more. The maps should be public domain because tax dollars were used to create the maps. The State of California struck up a deal with the federal government to freely store these maps on a server at UC Davis, and freely distrubute.
Here you can download all of the topo maps of Calfornia for free. Due to diferences between the NAD27/WGS84 datums (what the topo maps are based on)and the State datum (what the "property line" of the state is based on), the southern edge of Oregon and the western edge of Nevada are also included. There are also a lot more than just topo maps on the California Saptial Information Library's webpage, including bathymetric maps, satellite images, highway plans, census data, geopolitical maps, and much more. There are also several interactive mapping programs on the CaSIL webpage, including DRG Mapsurfer and Geofinder
These maps are located on the California Spatial Informaion Library's server at UC Davis.
These maps are UNtrimmed. They contain all of the margin data (such as scale, partial legend, datum and projection information, and relative location). If you would only like the trimmed versions to seamlessly collage, change the web address.
These maps are in GeoTIFF format. You will need to download a special viewer. I use OpenEV (available for Linux, Solaris, Windows and Irix) . For more information on the GeoTIFF image format, visit the "official" GeoTIFF website.