The abolitionist movements in the U.S. were significant as they sought to end the practice of slavery and promote racial equality. These movements gained momentum in the early to mid-19th century and involved various strategies, including petitions, publications, and public speaking. Key figures such as Frederick Douglass and Harriet Tubman played crucial roles in advocating for emancipation and the rights of African Americans. The abolitionist movements laid the groundwork for the Civil War and the eventual passage of the 13th Amendment, fundamentally changing the legal and social landscape of the United States.