15th Amendment
Image of the first few lines of the 15th amendment.

The 15th Amendment to the U.S. Constitution was aimed directly at curtailing attempts by the former Confederate states to exclude former slaves from voting and at the persistent violence over their political participation. It contains two short sections that prohibit the denial of the right to vote and allow Congress to enforce this prohibition.

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.

Section 2: The Congress shall have power to enforce this article by appropriate legislation.

The 15th Amendment was passed by Congress and submitted to the states for ratification on February 26, 1869 amid recurring bouts of violence against African Americans, particularly at polling locations.

Despite these incidents, the South was under much tighter Union control than earlier under the softer reconstruction in the immediate post-war period, and the ratification by the minimum three-fourths of the states was completed within a year. On March 30, 1870, the 15th Amendment was declared to have been ratified by the legislatures of twenty-nine of the thirty-seven existing states.

Texas voters approved a revised state constitution, as required under the Radical Reconstruction, and elected a state government in November 1869. The new Legislature convened and ratified the 13th, 14th and 15th Amendments to the U.S. Constitution, the final requirements for readmission to the Union. President Grant signed the act to readmit Texas to Congressional representation on March 30, 1870.

Source: University of Houston, Texas State Library and Archive Commission. (full source)