The Carousel in FantasyLand? I know they bought if fully assembled and moved it so maybe it was the quickest to put back together???
I was thinking in terms of attractions that came from the World's Fair. My other guess would have been the Hall of Presidents, but since you said ride, how about Dumbo's Elephants?
Let's go out on a limb...Tiki Birds! First animatronic at WDW?
Carousel of Progress - it was on display at the World's Fair.
Alright, two more guesses - Haunted Mansion or Space Mountain? As for the why, not sure.
Oh well, I looks like I was a minute late with the (short form) explanation. Stopher 1, good question!
Name the two tracks on Space Mountain
PS geo how was it