Found this interesting piece on the Anaheim Police Department's history page:
Civil disobedience during the late 1960s and early 70s was prevalent throughout the United States. The City of Anaheim was not spared their share of these disturbances. On August 6, 1970, Disneyland was the unlikely location for an event referred to as "Yippie Day." Towards the summer of 1970, thousands of flyers were being distributed, and advertisements were placed, in the Los Angeles Free Press inviting "Yippies" to attend the First International "Yippie Pow Wow."
Publicity in the underground newspaper was high and approximately 100,000 leaflets were distributed throughout the nation. According to Police investigations, the leaflets were distributed and the event was coordinated from a residence in the 1200 block of West La Palma Avenue in Anaheim. Hippies were encouraged to attend this non-sponsored event "to liberate Minnie Mouse, have free rein of the park and infiltrate Tom Sawyer's Island." Warned that Disneyland would not allow the Yippies admission to the park without a ticket, the coordinators encouraged people to "tear down the walls." The LA Free Press warned its readers to prepare for a confrontation, advising that Anaheim Police Officers were under going riot training and may be heavily armed. With this information, the Anaheim police Department prepared for a major confrontation, working with their strategy for the unauthorized visitation of an anticipated crowd of 20,000 plus Yippies to the Magic Kingdom.
Officials with the Anaheim Police Department and other Orange County police agencies began training their officers in crowd control. On the morning of August 6, 1970, Anaheim Police and Disneyland personnel were prepared for the Yippie take-over. As the gates opened, 300 Yippies made their entrance into the park. Anaheim Police waited in riot formation behind Main Street while Disneyland administrators and cast members dealt with the small group of unruly hippies. Once inside the park, the Yippies received an unexpected confrontation from regular park guests. Disneyland personnel handled these minor confrontations as hundreds of police officers remained in the back lot. It appeared that Disneyland personnel had things well in hand and the day would remain relatively peaceful. As the day wore on, so did the emotions and tempers of the paying park guests and Yippies. The Yippies assembled on Main Street and tried to gain unity in an attempt to disrupt park activity and cause damage to the park. As security officers attempted to gain order, one of Disneyland's security officers was assaulted. At that point the police were called upon to evict the Yippies from the park. As park guests watched and cheered, hundreds of police officers marched onto Main Street in formation and began their slow and deliberate sweep to clear the unruly crowd.
Instead of departing, the Yippies broke up and spread throughout the park. Police remained in formation on Main Street as Disneyland personnel cleared the park section by section and declared the park closed for the day.
Disneyland was officially closed at 7:10 p.m. but police continued to deal with confrontations with Yippies on surrounding park properties, including the Disneyland Hotel. It was not until 11:50 p.m. that they were allowed to leave.
Aside from the Anaheim Police Department, over 200 additional police officers were utilized as the Orange, Westminster, Fullerton and La Palma Police Departments. Jailers, Cadets and Explorers assisted in booking prisoners and manning the command posts. The California Highway Patrol took charge of traffic surrounding the park, and other local police agencies remained on standby alert. Security in and around the Anaheim Police building was heavy, with armed officers standing guard at all entrances. Each police agency providing assistance incurred their own costs for providing personnel in this mutual aid response. Cost to the Anaheim Police Department alone came to a grand total of $62,930.