By the 1960s, the once tiny hamlet of Oakland had now developed into a major-league city, status that did not go unnoticed by the professional sports industry. In 1960, a group of local investors organized the Oakland Raiders to compete in the upstart American Football League. In 1967, the Oakland Oaks, replaced in 1971 by the Golden State Warriors, helped to initiate the fledgling American Basketball Association. Expansion of the National Hockey League brought the Oakland Seals and ice hockey to the Coliseum Arena before that franchise left for Cleveland in 1976. In 1968, a year tarnished by the assassinations of Martin Luther King, Jr. and Robert F. Kennedy and large-scale urban riots throughout the country, the colorful Chicago-based car dealer, Charles O. Finley, moved his Kansas City Athletics to town and by 1972 the city had its first major-league championship when that "Swingin' A's" team won its first World Series.