The march from Selma to Montgomery was one of the most important and significant events of the Civil Rights Movement. It was absolutely vital in getting the Voting Rights Act of 1965 (one of the two most important accomplishments of the movement) passed by Congress. In this way, it did a great deal to foster the cause of the movement.
The main reason for the importance of this march was the response that it got from the white authorities. A large number of state troopers, along with a volunteer posse led by Sheriff James Clark met marchers as they left Selma. The marchers were attacked violently, with about 80 marchers ending up needing medical treatment. The violent attack on peaceful demonstrators aroused the sympathy and anger of people around the country. Soon after these events, President Johnson made a speech referring to the marches and promoting their cause. This helped to lead to the passage of the Voting Rights Act a few months later.
By helping to lead to the passage of the Voting Rights Act, these marches were a huge help to the Civil Rights Movement.