President Lyndon B. Johnson played a significant role in advancing civil rights for African Americans during his time in office. He signed the Civil Rights Act of 1964 into law, which outlawed discrimination based on race, color, religion, sex, or national origin and was a major victory for the Civil Rights Movement. Johnson also signed the Voting Rights Act of 1965, which aimed to overcome legal barriers at the state and local levels preventing African Americans from exercising their right to vote. These landmark pieces of legislation were crucial in the fight for racial equality and justice in the United States.