Much of the long-shot footage of the Chicago Fire is actually tinted stock footage from Chicago (1938).
The time travel computers and control panels at the mansion were previously used in Time Tunnel (1966), another Irwin Allen time-travel series.
The outdoor set of 1871 Chicago was actually the circa-1890 New York street set built for "Hello, Dolly!" (1969).
Francine York said years later that casting Sam Groom and Tom Hallick as the leads was a huge mistake because they were just "freakin' boring, really boring."
This was a pilot produced by Irwin Allen that wasn't picked up as a series.