Google Earth

BING’s Zoom Earth

USGS Map Locator

Historic Map Works

Old Maps Online

Sanborn Maps (This link takes you to Library of Congress. Not all Sanborn maps are included as this is a paid service. Official site here.) Here is a key to Sanborn Maps.

Library of Congress Maps

Historic Cities

USGS Topo Locator

USGS TopoView (awesome)

MyTopo

Historical Aerials

Anyplace America Topos

Acme Maps w Topo

Topographic map symbols

Old Maps

PastScape

Bluesky Mapshop

LIDAR Open Data Maps

UK LiDAR Resource

Gilmer Civil War Maps

Rare Map Collection

Making of America

West Point

Confederate Maps

More Confederate Maps