On June 2, 1924, President Calvin Coolidge signed the Indian Citizenship Act (also known as Snyder Act), which made all Native Americans American citizens. From the article:
"The Indian Citizenship Act of 1924, also known as the Snyder Act, granted full U.S. citizenship to Native Americans. While the Fourteenth Amendment to the U.S. Constitution, ratified in 1868, had bestowed citizenship on all persons born in the United States—including formerly enslaved people—the amendment had been interpreted as not applying to Indigenous native people. Enacted partially in recognition of the Native Americans who had served in World War I, the act was signed into law by President Calvin Coolidge on June 2, 1924. Though the act granted Native Americans U.S. citizenship, it did not ensure them the right to vote."