July 17, 1955, was intended as an invite-only, media-oriented day to celebrate the long-awaited opening of Disneyland. Technically it was called the “international press preview,” but Disney employees—and even Walt Disney himself—would afterwards come to label it “Black Sunday.”

During the 1930s and 1940s, Disney had visited several amusement parks with his wife and their two daughters, noticing that the majority tended to be rundown, trash-littered places that usually focused on scary thrill rides. He envisioned something better.

In 1948, he sketched out a small park that he dubbed “Mickey Mouse Park.” Its primary attraction was to be a boat ride, but over the years, his plan morphed into a spectacular venue that would draw people from around the world.

To raise the cash to bring this place to life, Disney sold his vacation home and borrowed against a life-insurance policy. Then, in October 1954, the fledgling ABC-TV network helped by offering priceless promotion for Disney’s dream through an hour-long Wednesday-night show called “Disneyland.”

In 1953, Disney purchased 160 acres of orange and walnut trees near the farming town of Anaheim, 22 miles southeast of downtown Los Angeles. With a crew of 1,200 workers, construction began the next year. By opening day in 1955, Disneyland’s price tag had reached $17 million (about $125 million in today’s money).

Disneyland officials expected 15,000 of their invited guests to show up for the opening, however, over 28,000 excited folks, many wielding counterfeit tickets, jammed into the overcrowded park that day. One enterprising man charged $5 to people who wanted to climb a back fence by using a ladder that he brought.

Much to Uncle Walt’s chagrin, his troubles that day were just beginning. Around the park, workers frantically slathered on paint and hastily planted trees. Many rides were still under construction, and those that operated sometimes broke down. Too many passengers aboard the Mark Twain Steamboat nearly caused it to capsize. Every park restaurant and concession stand ran out of food and beverages within hours. A small fire broke out in Sleeping Beauty’s Castle. Adventureland, Frontierland and Fantasyland had to shut down for the afternoon due to a gas leak.

The temperature that afternoon reached a sweltering 101 degrees, with the now-sticky fresh asphalt seizing women’s high-heeled shoes. While drinking fountains were available around the park, none worked on that fateful day. Plumbers had gone on strike, and Disney had to choose between working water fountains and working toilets.

“Well, you know they could drink Coke and Pepsi,” he grumbled, “but they can’t pee in the streets. Finish the restrooms.”

After opening day, adult park visitors paid a $1 admission fee—kids were 50 cents—while the park’s 35 rides each carried a separate cost of 25 to 35 cents each per adult, with children paying 10 to 25 cents each.

Two months later, the Magic Kingdom had welcomed its one-millionth customer, the debacle of Black Sunday mercifully forgotten.