This ad in the December 14, 1962 Albuquerque Journal (Albuquerque, NM) shows the X-20 Monorail toy, selling for $5.97.
An amazing invention that's fun for everyone . . . the HO Gauge Monorail. Thrilling speeds on a single rail, carries messages to neighbor's house, travels long distance. Deluxe set includes self-propelled battery-operated monorail engine, 40 ft. flexible aerial track with curve support, 15 ft. of monorail track, 10 monorail suspension towers, variable speed control tower and more.
Those of you intrigued by the half turtle, half frog, Odd Ogg can read more about him at Older Than Me.
Frederick & Nelson Ad (1962)
Closer Than We Think! Monoline Express (1961)
Amphibian Monorail (Popular Science, 1934)
Monorails at Disneyland (1959 and 1960)