The 15th Amendment, 1868 | Records of Rights

Section 1. The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of race, color, or previous condition of servitude. Denying the right to vote based on sex, however, was not prohibited.
Section 2. The Congress shall have power to enforce this article by appropriate legislation. The assertion that the Federal Government had the power to enforce the 14th and 15th Amendments and to protect the rights of individuals was a radical departure.

The 15th Amendment 1868

For a brief period after the 15th Amendment was ratified, African Americans experienced real political power. Thousands of former slaves were elected to public office, from the local level all the way up to the United States Senate.

National Archives, General Records of the U.S.Government