You really can't get more forgotten than this. It's a TV show that’s barely listed in the IMDB* and without an entry in Wikipedia (as of this writing), and it's only mentioned in passing on the web. It took me two days of searching before I could find an episode list online (Since taken down). But it was one of the high points of TV, even if few people saw it. "Off the beaten path" indeed.
Back in the late 60s, NBC was faced with a problem. They wanted to provide late Sunday afternoon programming, but, after the football season ended, there were no sports to run (they didn't have the right to the NBA, the NHL was too much of a niche market, and junk sports hadn't been invented). So the network took a bold step: a limited series (as we'd call it today) of one hour, with drama, comedy, and documentaries -- presented without commercials. It was the unusual case of a network putting prestige ahead of profit.
The show was filled with recognizable names, both established or on their way to becoming well known. Some of the actors involved were Yaphet Kotto, Jo Van Fleet, Frank Langella, Nanette Fabray, Fritz Weaver, Bernadette Peters, Verna Bloom, Frank McHugh (a favorite of mine from the 30s), Jack Gilford, Nancy Walker, David Steinberg, Mildred Dunnock, Donald Pleasance, Richard Briers, John Gielgud, George Plimpton, Christopher Plummer, and Diana Rigg. Some of the plays were written by such people as Jim Henson, Tom Stoppard, Harold Pinter, John Guare, and novelist John Hawkes. Documentaries featured people like Marshall McLuhan (they had him right there, though he evidently didn't like the result), Frederico Fellini, Arthur Penn (shown directing deaf actors), L'il Abner's Al Capp, and the Beatles.
The show ran at various times on Sunday afternoons, as early as 3:00 pm and as late as 5:00. Twice it preempted Star Trek to run on Friday nights. (I guess it was a sure sign that StarTrek was on the way out that they replaced it with a commercial-free show.)
Not everything was commissioned by NBC; several episodes were the first American showing of BBC programmes. The Beatles were shown rehearsing "Hey, Jude" as a part of a show on music in Britain, hosted by Alistair Cooke (before he became connected with PBS). The Pinter show -- short animations scripted by him, with a look at to how they were made -- starred several big British stars, and the Stoppard play, The Engagement, was made in the UK, probably for the BBC (and got theatrical release), but was shown in the US first.
One of the more memorable efforts was The Cube, a surrealistic comedy-drama written and directed by Jim Henson. No Muppets, but a strange story of a man trapped in a white cube, with people dropping by. Henson also directed Youth '68 for the series, a documentary about the youth culture of the time.
Of course, things had to come to an end. Though the show was well regarded (it won a Peabody Award in 1969), by definition, any show on a network that ran without commercials is losing money. The final season consisted on reruns, plus a documentary on Buckminster Fuller. In addition, PBS was growing, and was a more natural fit for the type of programming the show offered. Once NBC figured out how to put sponsored programming on Sunday, it was the end. Prestige only goes so far.
*It was not when I first wrote this entry.