while unfurling Viet Cong and Youth International Party flags. Standby riot police entered and the park was evacuated around 5:00 p.m. when some of the insurgents approached the park's Bank of America branch, sparking concern that the building could be burned in a similar fashion to the arson of a Bank of America in Isla Vista in February 1970. Police arrested 23 park guests and it was only the second unexpected early closure in park history, the first being in response to the assassination of John F. Kennedy in 1963. The incident was cited as a clash of the park management's perceived appeal to tradition following the death of Walt Disney and the growing counterculture movement among young people in the United States. Despite the opening of the more expansive Walt Disney World resort in 1971, Disneyland continued to set attendance records and maintained its status as a major tourist attraction. In 1972, the Bear Country land was opened and the Main Street Electrical Parade was introduced. Disneyland underwent several changes in preparation for the United States Bicentennial. In 1974, Walt Disney's Carousel of Progress was replaced with America Sings, an audio-animatronic theater show featuring the history of American music. America on Parade debuted in 1975 and ran through 1976 in celebration of the bicentennial. Several of the park's earliest attractions received major changes or were replaced in the mid-to-late 1970s. The Flight to the Moon attraction was rethemed as Mission to Mars in March 1975, five years after Apollo 11 had successfully landed humans on the moon. Construction of Space Mountain began that same year adjacent to the new Mission to Mars attraction but was delayed by El Niño-related weather complications. The ride opened in 1977 to much acclaim as lines would often stretch all the way to Main Street, U.S.A. The final major change of the decade came in 1977 when the slow-paced Mine Train Through Nature's Wonderland was closed and replaced by the similarly-themed Big Thunder Mountain Railroad rollercoaster in 1979. 1980s Fantasyland was closed for refurbishment in 1982 and reopened to the public in 1983 as "New Fantasyland." On December 5, 1985, to celebrate Disneyland's 30th year in operation, one million balloons were launched along the streets bordering Disneyland as part of the Skyfest Celebration. 1990s In the late 1990s, work began to expand the one-park, one-hotel property. Disneyland Park, the Disneyland Hotel, the site of