The crew of Los Angeles County Fire Department Station 51, particularly the paramedic team, and Rampart Hospital respond to emergencies in their operating area.

The series initially starred veteran movie supporting actor Ward Bond as the wagon master, later replaced upon his death by John McIntire, and Robert Horton as the scout, subsequently replaced by lookalike Robert Fuller a year after Horton had decided to leave the series. The series was inspired by the 1950 film Wagon Master directed by John Ford and starring Ben Johnson, Harry Carey Jr. and Ward Bond, and harkens back to the early widescreen wagon train epic The Big Trail starring John Wayne and featuring Bond in his first major screen appearance playing a supporting role. Horton's buckskin outfit as the scout in the first season of the television series resembles Wayne's, who also played the wagon train's scout in the earlier film.