What was the importance of the 15th amendment to the civil rights movement?

The fifteenth Amendment of the United States Constitution granted African American males the right to vote by stating that an American citizen's rights could not be infringed upon on the basis of a man's race or a colour.

However, it is important to consider the fact that, although this amendment was passed, it was not heavily enforced and many African American men were still denied the right to vote, especially in southern states.