Sanborn Maps
Public Library Database
http://library.lclark.edu/reference/resourcedisplay.php?subject=Public_Library_Databases

The Sanborn Fire Insurance Maps provide digital access to more than 660,000 large-scale maps of more than 12,000 American towns and cities. Details of street patterns, lot lines, and the placement, size, shape, construction materials, and use of buildings in American cities are included.