The significant legislative act that abolished slavery in the United States in 1865 was the 13th Amendment. Ratified on December 6, 1865, it legally ended the institution of slavery and involuntary servitude, except as punishment for a crime. This amendment represented a monumental shift in American society following the Civil War and marked a crucial step toward civil rights for formerly enslaved individuals. The 13th Amendment laid the groundwork for subsequent amendments and legislation aimed at securing equal rights and protections for all citizens, particularly African Americans, though the struggle for full equality continued long thereafter.