http://freegeographytools.com/2007/downloadable-large-format-historical-maps
This site provides links to many high resolution historical and current maps. It provides links to sources such as: Library Of Congress, Perry-Castaneda Map Library, Leen Helmink, Yale University Map Library, University Of Connecticut, Atlas Of Canada, Michigan State University, Quebec National Library And Archives, and W. M. Keck Earth Sciences and Mining Research Information Center.