Martin Luther King Jr., who had won the 1964 Nobel Peace Prize for his efforts to achieve equality of the races, was assassinated in 1968. Following his death others led the movement, most notably King's widow, Coretta Scott King, who was also active, like her husband, in the Opposition to the Vietnam War, and in the Women's Liberation Movement. There were 164 riots in 128 American cities in the first nine months of 1967. Frustrations with the seemingly slow progress of the integration movement led to the emergence of more radical discourses during the early 1960s, which, in turn, gave rise to the Black Power movement of the late 1960s and early 1970s. The decade would ultimately bring about positive strides toward integration, especially in government service, sports, and entertainment. Native Americans turned to the federal courts to fight for their land rights. They held protests highlighting the federal government's failure to honor treaties. One of the most outspoken Native American groups was the American Indian Movement (AIM). In the 1960s, Cesar Chavez began organizing poorly paid Mexican-American farm workers in California. He led a five-year-long strike by grape pickers. Then Chávez formed the nation's first successful union of farm workers. His United Farm Workers of America (UFW) faltered after a few years but after Chavez died in 1993 he became an iconic "folk saint" in the pantheon of Mexican Americans.