Final answer:
The Fifteenth Amendment addressed post-Civil War racial inequalities by granting African American men the right to vote, the Nineteenth Amendment secured women's suffrage, the Twenty-Sixth Amendment lowered the voting age to eighteen, and the Twenty-Fourth Amendment abolished poll taxes.
Step-by-step explanation:
There are four Amendments that expand suffrage nationally, each emerging from a critical period in U.S. history to promote the principles of democracy and justice. The Fifteenth Amendment was one of the Reconstruction Amendments, ratified in 1870, which granted African American men the right to vote, attempting to address the inequalities that persisted after the Civil War.
The Nineteenth Amendment marked a significant victory in the women's suffrage movement when it was ratified in 1920, ensuring that the right to vote could not be denied on the basis of sex. In the midst of the Vietnam War, the Twenty-Sixth Amendment was passed in 1971, lowering the voting age from twenty-one to eighteen, a reflection of the sentiment that those old enough to be drafted for war should also have a voice in the political process through the right to vote. Lastly, the Twenty-Fourth Amendment, ratified in 1964, eliminated poll taxes, which were a financial barrier to voting, particularly for African Americans in the South.