When WDW opened it was just MK. It had Jungle Cruise, SWF Treehouse, I'm pretty sure Tiki Room, CB Jamboree, Hall of Pres, Tom Sawyer Island, Haunted Mansion, Small World, 20,000 Leagues, Mr. Toad - Snow White - Peter Pan, Fantasy Faire (live shows), Mickey Mouse Review, America the Beautiful (360 theatre), Mission to Mars (I think this was the first exhibit in what is now the Alien Encounter), Race Track. It also had Skyway (from Fantasyland to Tomorrowland) which doesn't exist now.
I think Space Mtn and Pirates were the first exhibits to open after the initial park opened. I'm not sure whether people mover opened with Space Mtn or was there from the beginning.
I think Carousel of Progress was soon after that. Then Tunder Mtn. Splash Mtn came a while later.
I have some old brochures from the 70's, and some old tickets (the old A-E tickets had the names of the rides on them). I'll have to check them to see which I left out. (I didn't mention A and B rides.)