The Magic Kingdom opened with 22 (26 if you count the Main street vehicles seperatly) attractions
In Adventureland:
Jungle Cruise
Sunshine Pavilion /Tropical Serenade
Swiss Family Tree House
In Fantasyland:
Cinderella's Golden Carrousel
Dumbo Flying Elephants
it's a small world
Mad Tea Party
Mr. Toad's Wild Ride
The Mickey Mouse Revue
Skyway to Tomorrowland
Snow White's Adventures
In Frontierland:
Country Bear Jamboree
Mike Fink Keel Boats
Davy Crockett's Explorer Canoes
Frontier Shooting Gallery
In Liberty Square:
Diamond Horseshoe Revue
Hall of Presidents
Haunted Mansion
On Main Street U.S.A.
Main Street Vehicles (Horseless Carriage, Jitney, Fire Truck, Trolley, & Omnibus)
Main Street Cinema
Walt Disney World Railroad (Main Street & Frontierland Stations only)
In Tomorrowland:
Grand Prix Raceway
Skyway to Fantasyland
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By the time Roy Disney dedicated the park on October 25th 1971 several other attractions had made their debut.
Admiral Joe Fowler Riverboat - October 2nd
Peter Pan's Flight - October 3rd
20,000 Leagues Under the Sea - October 14th