

These links allowed stations to share television programs across great distances, and allowed advertisers to air commercial advertisements nationally. In the 1940s, four television networks began operations by linking local television stations together via AT&T's coaxial cable telephone network. The October 1986 launch of the Fox Broadcasting Company was met with ridicule despite the industry skepticism and initial network instability, the Fox network eventually proved profitable by the early 1990s, becoming the first successful fourth network and eventually surpassing the Big Three networks in the demographics and overall viewership ratings by the early 2000s. Founded in 1953, it slowly grew into the National Educational Television or NET network and then was superseded by PBS by 1970. The first lasting attempt at a fourth network as DuMont went into decline was arguably the Educational Television and Radio Center (ETRC). Television critics also grew jaded, with one critic placing this comparison in the struggles of creating a sustaining competitor to the Big Three, "Industry talk about a possible full-time, full-service, commercial network structured like the existing big three, ABC, CBS and NBC, pops up much more often than the fictitious town of Brigadoon." After decades of these failed "fourth networks", many television industry insiders believed that creating a viable fourth network was impossible. However, between the 1950s and the 1980s, none of these start-ups endured and some never even launched. Many companies later began to operate television networks which aspired to compete against the Big Three.

Never able to find solid financial ground, DuMont ceased broadcasting in August 1956. television industry was in its infancy in the 1940s, there were four major full-time television networks that operated across the country: ABC, CBS, NBC and the DuMont Television Network. television from the 1950s to the 1980s: ABC, CBS and NBC.

In American television terminology, a fourth network is a reference to a fourth broadcast (over-the-air) television network, as opposed to the Big Three television networks that dominated U.S. For the proposed UK television service in the 1960s and 1970s, see Fourth UK television service. This article is about the situation in the United States.
