DuMont was the first and the only one to truly achieve network status, but there were lots of other attempts, some in partnership with major studios (relationships the FCC tended to frown upon back when the FCC had frowning muscles). All of these are vanishingly obscure now. I'd entirely forgotten about NTA until I came across a reference to it looking up when rural states got their first TV stations.
The NTA Film Network was an early American television network founded by Ely Landau in 1956. The network was not a full-time television network like CBS, NBC, or ABC. Rather, it operated on a part-time basis, broadcasting films and several first-run television programs from major Hollywood studios. Despite attracting over 100 affiliate stations and the financial support of Twentieth Century-Fox (which purchased a 50% share of NTA in November 1956) the network proved unprofitable, and was discontinued by 1961. The NTA Film Network's flagship station, WNTA-TV, is now WNET, one of the flagship stations of the Public Broadcasting Service (PBS).Most of the original programming was deeply forgettable, but there were some notable exceptions, such as Mike Wallace's first national show and the still impressive Play of the Week.
In October 1956, NTA launched the NTA Film Network, a syndication service which distributed both films and television programs to independent television stations and stations affiliated with NBC, CBS, or ABC (DuMont had recently gone out of the network business). The ad-hoc network's flagship station was WNTA-TV, channel 13 in New York. The NTA Network was launched as a "fourth TV network", and trade papers of the time referred to it as a new television network.
Unlike the Big Three television networks, the local stations in the NTA Film Network were not connected via coaxial cable or microwave relay. Instead, NTA Film Network programs were filmed and then mailed to each station in the network, a method used by television syndicators in the 1950s and 1960s. However, many local stations agreed to broadcast NTA Film Network programs in pattern (simultaneously). Landau's claim to network status was based on the simultaneous airing of the programs.
The NTA Film Network launched on October 15, 1956, with over 100 affiliate stations. In November 1956, it was announced that 50% of the network had been purchased by Twentieth Century-Fox, which would also produce original content for the network. The film network grew to 128 stations. In September 1957, the network purchased KMGM-TV (now Fox O&O KMSP-TV) in Minneapolis.
The NTA Film Network aired both films and television series. Among its 1956–1957 offerings were 52 Twentieth Century-Fox films. Premiere Performance, a prime time block of Twentieth Century-Fox films, aired from 1957–1959. Other film blocks included TV Hour of Stars and The Big Night (both 1958–1959).