Today is the 55th Anniversary of the first big expansion of Disneyland - the day when the E-tickets were introduced with the Monorail, Matterhorn and Submarine Voyage all opening.
The Disney Parks Blog has an excellent article with photos from that day available online here: http://disneyparks.disney.go.com/blog/2 ... land-park/
Considering all three attractions are still with us (for the time being anyway!) I'd say Walt's investment in those three items have probably paid off