What was Dwight Eisnehower's greatest accomplishment?

Answer 1

The Interstate Transportation system will be his legacy. The Federal Aid Highway Act which created the Interstate Highway system was the major legislation during his administration.

As a bill in Congress, the FAHA was promoted as the "National Interstate and Defense Highways Act of 1956," primarily because its backers understood that federal involvement in highway construction was unconstitutional unless it could somehow be made to reflect a legitimate concern for a constitutional national concern, such as the "national defence," as the phrase exists in the Preamble to the US Constitution. Rumors circulated then -- and persist today -- to the effect that one mile in every five miles of interstate highway is straight and level enough to land a military aircraft on; this is simply not true, as anyone who has traveled the West Virginia Turnpike (I-64/I-77/I-79), among other stretches, will readily testify.

Bridge/overpass/tunnel heights for the original system were, however, set in order to provide clearance for highway-borne military missile transport, not commercial tractor-trailers.