Under coronavirus pandemic guidelines, "The Happiest Place on Earth" was opened only to California residents and capacity was limited to 25% to allow for social distancing.
There will be no parades, and the nightly fireworks displays have been put on hold to prevent crowds from gathering closely together.
Tickets to Disneyland are sold out through mid-June, according to the park's online reservation system, but there is more availability in the adjacent California Adventure.
Walt Disney Co closed its theme parks around the world in March 2020 to help curb the COVID-19 pandemic.
The company's most-visited resort, Walt Disney World in Orlando, Florida, reopened in July 2020.
Disneyland Paris is currently closed. Disney parks in Shanghai, Tokyo and Hong Kong are open.
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