Episode "Cavalry's Coming" of the western-sitcom "Dusty's Trail", which was created by the same person as "Gilligan's Island" and "The Brady Bunch". ************************************ Info from Wikipedia: Dusty's Trail was a 1973-1974 syndicated television series set in the 1800s about a small group of travelers separated from their wagon train who become lost. Dusty's Trail stars Bob Denver as Dusty, the assistant to the leader of a wagon train, and Forrest Tucker as Mr. Callahan, his irascible boss. Twenty-six episodes of the series were produced.
