Westerns were big as the 60's began. Perhaps, a little too big.
There were so many series of the genre on the air that inevitably there would be shows that deserved to continue for another season, but couldn't because of the glut that the networks themselves caused and couldn't stop.
One such example is Four Star's Stagecoach West, which was the studio's, and ABC's, for that matter, answer to Wagon Train, which at the time aired on NBC (and would later move to ABC). It was an hour in length, as opposed to most others being a half-hour. Stagecoach is likened to Wagon Train because of its' quasi-anthology format. That is to say, there were regular characters, but the episodes would showcase incidentals on a week-to week basis. 38 episodes were produced, which, by today's standards, would suggest Stagecoach would've been renewed, then cancelled halfway through its second season.
Both leads went on to bigger and better things. Robert Bray, for example, would resurface on Lassie, and spend 5 seasons there, while Wayne Rogers landed the plum role of his career as "Trapper" John McIntyre on M*A*S*H from 1972-5 before making the ill-advised decision to leave and return to drama. His 1st post-M*A*S*H entry, City of Angels, ended up just like Stagecoach West, cancelled after 1 season, because by then, the glut consisted of crime dramas instead of Westerns.
Following is the episode, "Dark Return":