The influential civil rights leader known for their speeches and activism is Martin Luther King Jr.. His advocacy for nonviolent resistance and social justice during the civil rights movement was marked by powerful speeches, such as "I Have a Dream," delivered during the 1963 March on Washington. King championed the struggle against racial segregation, discrimination, and injustice, emphasizing the importance of equality and brotherhood. His commitment to peaceful protest and dialogue helped galvanize public support for civil rights legislation and significantly advanced the cause of racial equality in America.