The Disneyland Monorail System (originally, the Disneyland ALWEG Monorail) opened on June 14, 1959, as a sightseeing attraction in Tomorrowland in Disneyland. The Mark I trains (Red and Blue) consisted of 3 cars each. With the debut of the 4-car Mark II in 1961 (and the new Yellow train), the track was lengthened to leave the park and stop at a station at the Disneyland Hotel. The monorail trains reached their current length of 5 cars in 1968 with the arrival of the Mark III. More streamlined and efficient than the Mark II, the Mark III also included the arrival of Monorail Green. There were two forms of access to the monorail. Persons who were leaving the park or persons at the hotel who had purchased tickets to enter the park could purchase a single ticket to go to the hotel or from the hotel to the entrance in Tomorrowland, respectively. Persons who had not purchased admission to the park could purchase a ticket to ride the monorail from the hotel station, into the park, and back to the hotel station. To prevent them from entering the park without paying, persons buying a monorail ticket who did not have a park admission would be loaded in a separate compartment which would remain locked until the monorail returned to the hotel.

Walt Disney originally envisioned the monorail as a practical form of public transport for the future. Unfortunately, the monorail came about during a time when America's - and particularly Los Angeles' - love affair with the automobile was increasing, and monorails in the United States came to be associated only with Disney's theme parks.

By the early 1980s, the Mark III trains were showing their age and the wear of years. In 1985, Disneyland began phasing out the Mark III trains one by one. The older trains were stripped to the chassis and rebuilt as Mark V trains. The Mark III Green went first, to become the Mark V Purple followed by the Mark III Yellow becoming the Mark V Orange. The Mark III Blue remained blue (albeit a lighter shade) and the last was Red, remaining Red. The notable difference was the loss of the bubble-top driver's area in favor of a streamlined "Learjet" look similar to the Mark IV trains at the Walt Disney World Resort. The new trains also sported closed passenger compartments (with open-able windows) and pneumatic doors. Following the 1985 Disney World monorail fire, a safety handrail was added along the spine of the train, as well as emergency fire exit hatches leading to the roof. The attraction's name remained the "Disneyland Monorail System", as it had been painted on the Mark III trains' skirts. The Mark V trains were built by Ride & Show Engineering, Inc. incorporating bodies that were produced by Messerschmitt-Bolkow-Blohm of Germany. Purple first made her appearance for testing in Autumn of 1986 and began regular operations a few months later. Orange was delivered in late Summer of 1987, followed by Blue in early 1988. The oldest train, Red, was also the last to be removed from the line for refurbishment in the Spring of 1988.In 1999, the monorail began lengthy periods of closures due to construction of Disney California Adventure theme park, which the Monorail beamway passed through. Although the beamway's route was not altered, a significant amount of construction was done around the existing beamway, and much of the terrain under the beamway's support columns was regraded, necessitating the closures. Additionally, the Disneyland Hotel station was completely demolished and a new station built in the same location. The system began limited operations in 2000, when the Downtown Disney Station became operational, but a significant portion of the beamway was still unusable due to construction. In 2001, the monorail resumed full capacity operations, passing through the new park, as well as the hotel within the park, Disney's Grand Californian Hotel & Spa.

In 2004, Monorail Orange was removed from the line and taken to Walt Disney Imagineering in Glendale to be reverse engineered. Monorail Blue was removed in September 2006 for rebuilding. The monorail was closed from August 21 through late December 2006 to prepare for the opening of Finding Nemo Submarine Voyage in 2007.

The refurbishment from Mark V to Mark VII was done one train at a time. The first Mark VII train, Monorail Red, arrived at Disneyland on December 20, 2007. It was originally expected to be in service by the end of February 2008, but due to design change issues, it did not begin servicing park guests until July 3, 2008. Mark VII Blue arrived on-site on April 10, 2008, began daytime riderless testing on August 1, 2008, and began guest service on September 16, 2008. Monorail Mark VII Orange arrived on-site on August 14, 2008, began riderless testing in March 2009, and began guest service on April 7, 2009. Monorails Red, Blue, and Orange make up the entire Mark VII fleet.