Walt Disney's Carolwood Pacific Railroad entertained weekend visitors until 1953, when a guest drove the Lilly Belle locomotive too fast around a curve, derailing it and injuring a child. Disney shut down his backyard railroad that day. But Roger Broggie, head of the Walt Disney Studios machine shop, saw a bigger opportunity. When Disney consulted him about including miniature trains in a studio tour, Broggie suggested making them full-sized instead. Construction of Disneyland's railroad began in August 1954. The two original locomotives cost over $40,000 each - significant money in the 1950s - and were assembled in a roundhouse that a former Navy rear admiral built in just one week. The trains that rolled out bore the name Retlaw: Walter, backward, a subtle mark of Disney's personal ownership through his company WED Enterprises.

On July 17, 1955, Walt Disney himself drove locomotive No. 2 into Main Street Station with California Governor Goodwin Knight and Santa Fe Railway president Fred Gurley riding in the cab. Art Linkletter and a young Ronald Reagan waited on the platform as television cameras broadcast the moment nationwide. The Santa Fe railway had paid $50,000 annually to sponsor the railroad, lending its name until 1974. From that opening day forward, the Disneyland Railroad required premium tickets - first C tickets, then D tickets, and finally the legendary E tickets that marked Disneyland's most coveted attractions. The railroad became one of the most popular steam-powered operations in the world, eventually carrying an estimated 6.6 million passengers each year around its circular route.

Disney initially wanted to buy existing miniature locomotives, but when collector Billy Jones refused to sell, Roger Broggie convinced him they could scale up the design of the backyard Lilly Belle instead. Two locomotives were built from scratch; three more came from unexpected places. No. 3 had worked as a sugar cane mill switcher in Louisiana since 1894. No. 4 pulled tourist trains in New Jersey beginning in 1925. No. 5, named Ward Kimball after the Disney animator whose own backyard railroad inspired Walt, entered service in 2005 with gold-leaf Jiminy Cricket silhouettes on its headlamp. Ward Kimball's grandson Nate Lord became a Disneyland Railroad engineer in 2011, frequently driving his grandfather's namesake locomotive. The railroad also hosted Pixar director John Lasseter's private locomotive in 2005, when the elderly animator Ollie Johnston drove his former train three times around the park.

The eighteen-minute journey around Disneyland passes through two remarkable dioramas. The Grand Canyon Diorama, inaugurated in 1958 and blessed by a 96-year-old Hopi chief named Nevangnewa, features a painted canvas backdrop claimed as the longest diorama in the world, accompanied by Ferde Grofe's Grand Canyon Suite. The Primeval World Diorama, added in 1966 with dinosaur figures from the New York World's Fair, was one of the last additions Walt Disney oversaw before his death that December. At New Orleans Square Station, crews perform boiler blowdowns while passengers hear a telegraph clicking out Morse code: "To all who come to this happy place: welcome. Disneyland is your land." When the Mark Twain Riverboat passes alongside, the train and boat whistle Shave and a Haircut to each other across the water.

The Disneyland Railroad switched from diesel to biodiesel made from recycled cooking oil in 2009. It closed temporarily in 2016 for Star Wars: Galaxy's Edge construction, reopening with a new section called Columbia Gorge featuring the line's only left-hand turn. The original roundhouse was demolished, but the locomotives continue their daily circuits. Guests can request seats in the locomotive tenders or in the Lilly Belle parlor car, which features mahogany paneling, velour seats, and Disney family photographs. The railroad that began as a grieving man's farewell to his backyard hobby now carries millions through carefully crafted landscapes, dinosaur exhibits, and painted canyon walls. Every detail traces back to a teenager selling newspapers on Missouri Pacific trains, dreaming of the day he might drive one himself.