This act made all native americans citizens of the united states and able to vote

The Snyder Act of 1924

Explanation:

The Snyder Act of 1924 admitted Native Americans born in the U.S. to full U.S. citizenship. Though the Fifteenth Amendment, passed in 1870, granted all U.S. citizens the right to vote regardless of race, it wasn't until the Snyder Act that Native Americans could enjoy the rights granted by this amendment.