the NAACP calculates that lynchings reached their worst level in history, with almost 3,500 people, three-fourths of them black men, murdered. African Americans responded with two major reactions: the Great Migration and the civil rights movement. The Great Migration began during World War I, hitting its high point during World War II. During this migration, black people left the racism and lack of opportunities in the South and settled in northern cities like Chicago, where they found work in factories and other sectors of the economy. This migration produced a new sense of independence in the black community and contributed to the vibrant black urban culture seen in the emergence of jazz and the blues from New Orleans and its spread north to Memphis and Chicago. The migration also empowered the growing civil rights movement. While the movement existed in all parts of the United States to combat Jim Crow law policies, its focus was against the Jim Crow laws taking place in the South. Most of the major events in the movement occurred in the South, including the Montgomery bus boycott, the Mississippi Freedom Summer, the Selma to Montgomery marches, and the assassination of Martin Luther King Jr. In addition, some of the most important writings to come out of the movement were written in the South, such as King's "Letter from Birmingham Jail". As a result of the Civil Rights Act of 1964 and the Voting Rights Act of 1965, all Jim Crow laws across the South and elsewhere in the United States were dropped. This change in the South's racial climate, combined with the new industrialization in the region, helped usher in what is called the New South. Collapse of the Black Belt socioeconomic plantation system Economic historians of the South generally emphasize the continuity of the system of white supremacy and cotton plantations in the Black Belt from the late colonial era into the mid-20th century, when it collapsed. Harold D, Woodman summarizes the explanation that external forces caused the disintegration from the 1920s to the 1970s: When a significant change finally occurred, its impetus came from outside the South. Depression-bred New Deal reforms, war-induced demand for labor in the North, perfection of cotton-picking machinery, and civil rights legislation and court decisions finally... destroyed the plantation system, undermined landlord or merchant hegemony, diversified agriculture and transformed it from a labor- to a capital-intensive industry, and ended