Highway History
United States Federal Highway Administration page with a collection of some auto trail histories and other related information.
http://www.fhwa.dot.gov/infrastructure/history.htm
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| Travel Details & Reviews
North American Auto Trails
Catalog of auto trails from the United States and Canada in the 1910s and 1920s; includes route markers and current numbers.
http://www.marion.ohio-state.edu/fac/schul/trails/trails.html
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| Travel Details & Reviews