Kansas Interstate First?

[W. Gray]

Kansas claims to be the first state in the Union to have an interstate highway project completed. A section was completed just west of Topeka on September 26, 1956.

Or was it the first?

http://www.fhwa.dot.gov/infrastructure/rw96h.cfm

I might add that the four lane Pennsylvania Turnpike completed in 1940 was reduced to two lanes at all the mountain tunnels. The two lane tunnels created slower speeds and frequently a bottleneck. There were many tunnels through the Pennsylvania mountains. The Interstate project, constructed new tunnels and solved the problem.