California's Disneyland* opened in 1955 on 160 acres and today has 300 acres, but it sits in a developed area with no room to grow. (When the California Adventure theme park was added, it was built on a parking lot.)
Contrast this to Disney World. By 1959, Walt Disney knew he wanted a vast expanse when he went looking for his "Florida project". Walt Disney World has 43 square miles (over 30000 acres), much of it is still undeveloped. The first theme park, The Magic Kingdom, opened in 1971 and repeated many of Disneyland's highlights. Today, count up four theme parks, two water parks, 23 themed resorts, the Downtown Disney entertainment zone, and five golf courses. The Epcot theme park alone is 300 acres; Animal Kingdom, 500; Disney's Hollywood Studios, 135 acres; Magic Kingdom, 107 acres; and the two water parks, Blizzard Beach and Typhoon Lagoon, have 66 and 61 acres each. Disney World is in its own league on the planet.
Disneyland, meanwhile, has the original Disneyland Park plus the Disney California Adventure Park, which opened in 2001 with 67 acres but not much going on. Hence a $1.1 billion expansion that started in 2007, adding some excellent attractions. Disneyland also has a Downtown Disney area of shops and restaurants that connects the two theme parks, and three themed Disney resorts.
Continue to Reasons to Visit Disneyland
*Most people say "Disneyland" to refer to the entire Disney destination in Anaheim California. The official name, however, is the "Disneyland Resort" which includes the Disneyland Park (the original theme park), and the Disney California Adventure Park.