Actually there is a military connection to Route 66, in a round about way. A young Dwight Eisenhower wrote a paper just after the Great War that argued that the West Coast of the US was essentially indefensible due to the poor transcontinental road network. Eisenhower had taken part in an exercise where the US Army employed motor transport to conduct a crossing from one side of the US to the other. He later attributed this experience as being a major motivator in establishing the US interstate highway network during his presidency. Eisenhower signed over the funding in 1956.
The actual Route 66 was superseded by the Interstate Highway System, Eisenhower's project.