Voting Rights Amendment
This reconstruction amendment to the US Constitution was passed by Congress on February 26, 1869 and Ratified on February 3, 1870.
The 15th amendment extended the right to vote to African American men although it wasn't until later, the Voting Rights act of 1965, when they could actually vote without having to be subjected to poll taxes, literacy or rights tests, intimidation from the Klu Klux Klan or other radical groups, or other means.
Resolved by the Senate and House of Representatives of the United States of America in Congress assembled, (two-thirds of both Houses concurring) that the 15th amendment be proposed to the legislature of the several States as an amendment to the Constitution of the United States which, when ratified by three-fourths of said legislatures shall be valid as part of the Constitution. 
The passing of this amendment relates to the classification of slaves before the passing of the 13th Amendment in which slaves were only counted as three-fifths of a person. During this time, slaves had no rights and were not able to vote so their owners would get to use them to their advantage. The slave owners wanted all of the slaves population to be counted so that they could gain more representation through the US House of Representatives and Electoral College. Those who opposed slavery wanted as little as possible of the slave population to be counted so that those who did support slavery wouldn't have more representation. Since the 13th Amendment did pass and slavery was abolished, it lead to African Americans gaining more rights like in this Amendment where they were granted the right to vote.
"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."
"The Congress shall have power to enforce this article by appropriate legislation."