On April 6, 1917, the day the Senate ratified the declaration of war with Germany, Pres. Woodrow Wilson exercised a provision of the Radio Act of 1912 that enabled nationalization during a war; the Navy physically acquired radio companies, consolidated them and broke patents to stimulate innovation; it also took over around 50 commercial radio stations and closed down the rest of them (along with all amateur radio operators).

Source: Profits Over People: Why Weren't the Vaccine Manufacturers Nationalized? - CounterPunch.org