Which of the following extended voting rights to American women?

The 19th amendment is the correct choice because it specifically granted women the legal right to vote in the United States. Ratified in 1920, it states that the right to vote cannot be denied on the basis of sex, marking a significant achievement in the women's suffrage movement. This amendment was the culmination of decades of activism by women and supportive allies striving for equality in voting rights.

The other options do not extend voting rights to women in the same explicit manner. The 15th amendment addresses voting rights but focuses on race and does not include gender as a basis for voting eligibility. The Equal Rights Amendment, while aimed at ensuring equality under the law regardless of sex, was not passed by the necessary number of states to become an amendment and thus does not currently have legal standing. The Civil Rights Act primarily addresses discrimination in employment and public accommodations, not directly related to the enfranchisement of women.