Big Three television networks
The DuMont Television Network launched in 1944. The three networks once controlled a few television stations. After a while, they affiliated with other stations to cover almost the entire United States by the late 1950s. Most of these stations are affiliated somehow with all three major networks and DuMont in markets where only one or two television stations operated in the early years of commercial television. It made some TV shows hard to handle. As more stations signed on, ABC, NBC, and CBS could carry enough programming on one station.