Short answers, pulled from the story.
Walt Disney started planning Disneyland on the 31st of August 1948 when he sent a memo to studio production designer Dick Kelsey. The initial concept was called Mickey Mouse Park and envisioned a small play park near the Burbank studios across Riverside Drive.
The chaotic first day became known as Black Sunday despite being intended as an International Press Preview event. Approximately 28,000 people attended but rides broke down, restaurants ran out of food, and traffic delayed on Harbor Boulevard while heat intensified.
New Orleans Square arrived in 1966 followed by Bear Country in 1972 which is now called Bayou Country. Mickey's Toontown opened in 1993 and Star Wars: Galaxy's Edge debuted in 2019 within Black Spire Outpost village on planet Batuu.
Disneyland has had a larger cumulative attendance than any other theme park in the world with 757 million visits recorded by December 2021. In 2024 the park saw 17.33 million visitors making it the second most visited amusement park globally behind Magic Kingdom.
The park closed indefinitely starting the 14th of March 2020 due to the COVID-19 pandemic before reopening the 30th of April 2021. This closure was part of global health measures affecting all major entertainment venues during that period.