All fo these doofuses like to claim that they’re the first to receive federal approval to fly their contraption but none mention the Taylor Aero Car, designed and built by Molt Taylor in 1949. Though only 6 were produced, they received certification from the Civil Aeronautics Administration in 1956. Taylor made a deal with Ling Temco Vaught (LTV) to produce the Aero Car but the deal required him to secure 500 orders. He was only able to get about half that and so the deal fell through.
Here’s the wikipedia: https://en.wikipedia.org/wiki/Aerocar#Testing_and_certification