On that fateful day 50 years ago in Dallas, the future of the United States was thought to be at stake. Heightened security measures surrounded a newly sworn-in president, who was whisked from Texas aboard Air Force One, shadowed by Secret Service agents and the widow of John Fitzgerald Kennedy. In the ensuing weeks, the Warren Commission was established and a sullied Secret Service pondered how to better protect the 36th president of the United States while still allowing him the mobility to leave the White House. Transporting the president would never be the same. According to experts in presidential...