How did protest marches lead to the passage of the Voting Rights Act?

On March 7, 1965, civil rights supporters tried to march from Selma, Alabama to the state capital, Montgomery. Police officers and state troopers used violence to stop them. The event became known as "Bloody Sunday," and the violence horrified many Americans when it was broadcast on the evening news. Three weeks later, Martin Luther King led a successful march from Selma to Montgomery.

That same month, President Lyndon Johnson submitted the Voting Rights Act to Congress to guarantee that black Southerners would be able to vote. Congress soon passed the act. After a decade of legal and political struggle, the civil rights movement had achieved its goals of ending legalized segregation and ensuring the right to vote for black Southerners. The civil rights movement had achieved legal and political equality for black Americans. But the goal of economic and social equality for blacks was much more difficult to achieve.