"I speak tonight for the dignity of man and the destiny of democracy," President Lyndon B. Johnson declared before congress on March 15th, 1965.
"There is no Negro problem. There is no Southern problem. There is no Northern problem. There is only an American problem," he continued.
The brutal events were broadcast on live television and shook much of the nation. Civil rights activists traveled to Selma from all over the country to support the cause.
"There is no cause for pride in what has happened in Selma. There is no cause for self-satisfaction in the long denial of equal rights of millions of Americans," Johnson continued.
Although the Civil Rights Act of 1964 had ended segregation, many laws still existed making it difficult or impossible for minorities to register to vote -- especially in the South. Black voters could be required to pass a literacy test, or asked to recite the entire constitution among other tasks in order to register.
President Johnson spoke before the joint session to lay out his plan to introduce legislation protecting the voting rights of all Americans, regardless of their skin color.
"This bill will strike down restrictions to voting in all elections -- federal, state, and local -- which have been used to deny Negroes the right to vote," Johnson said. "It is wrong -- deadly wrong -- to deny any of your fellow Americans the right to vote in this country."
President Johnson signed the Voting Rights Act into law less than six months later, on August 6, 1965. Among other things, it outlawed literacy tests and required federal oversight in states that had used them.
In the 51 years since the law was passed, there have been a number of challenges to the law. Last year, a New York Times article detailing all of the challenges the law has faced gained so much attention President Barack Obama responded to it.
And in 2013, the U.S. Supreme Court struck down section 4 of the Voting Rights Act, calling it unconstitutional. The section required nine states with histories of voter suppression to get approval from the Justice Department in order to change voting laws.
Activists and politicians were outraged by the decision, and have spoken out about other perceived challenges to the Voting Rights Act -- including voter ID laws.
Voter ID laws, which require voters to have a valid government-issued ID, have become a heated and heavily-debated issue. Many Democrats call them discriminatory and against the Constitution, while Republicans say they are meant to prevent voter fraud.