Final answer:
Congress did indeed override President Andrew Johnson's vetoes of both the Freedmen's Bureau and the Civil Rights Act of 1866, marking a significant step in protecting the rights of all U.S. citizens, regardless of race.
Step-by-step explanation:
Yes, Congress did successfully override President Andrew Johnson's vetoes of the Freedmen's Bureau and the Civil Rights Act of 1866. Despite Johnson's veto of the Freedmen's Bureau extension in February 1866, Congress continued to challenge his authority, demonstrating their commitment to deciding the course of Reconstruction. Furthermore, after Johnson vetoed the Civil Rights Act in April 1866, Congress overrode his decision, marking the first time in history that a presidential veto was overturned.
This legislation was critical in establishing that "all persons born in the United States...of every race and color, without regard to any previous condition of slavery," were entitled to full constitutional protection. This Act also allowed federal intervention in states to ensure civil rights were upheld, setting a precedent for the future Fourteenth Amendment and challenging the Black Codes that aimed to maintain white supremacy after the Civil War.