Awesome question. I cannot cover the entirety of indigenous resistance in the U.S., that is a rich history and hopefully others will add more information from their areas of research, but I would like to dive into one of the forgotten organizations in the fight for indigenous civil rights: the Society of American Indians. For this entry I will rely heavily on Maroukis's We Are Not a Vanishing People: The Society of American Indians, 1911-1923. This is probably the single best overview of the SAI if you want to dive into the topic.

The Society of American Indians was established in 1911, and was the first influential national organization by, and for, American Indians. Per their statement of purpose,

The primary aim of the organization is to develop and organize men and women of Indian blood as wise leaders of their race.

And in their "General Statement" states

Through this Society the red man may break the long silence and voice his opinion and beliefs. The future of the Indian is thus placed in the hands of the Indian himself.

These reformers naturally built upon the foundation of previous movements, but the SAI was distinct in it's scope and accomplishments. The SAI held annual conferences, published quarterly journals, provided a platform for discussion of indigenous civil rights through publishing pamphlets and speeches, and maintained communication between leaders and government officials, including non-indigenous "friends of the Indians". They met with Presidents Taft, Wilson, and Harding and traveled the country to raise support for their efforts.

Part of the erasure of much of the SAI in modern discussion of indigenous civil rights concerns the apparent embracing of assimilation policies common to the era. Many of the founding members of the SAI were among the first generation to attend boarding schools, and wrote extensively during the Progressive Era. By necessity to garner further support, they needed to write/speak to their larger American audience using the language of the time. Previous scholars dismissed the impact of the SAI due to this superficial adoption of Progressive Era language of acculturation, but subsequent investigations are now re-analyzing how the SAI resistance was tribal-centered and predicated on self-determination. These themes, especially self-determination, would be carried forward with the AIM and further indigenous civil rights movements.

Of chief concern to the SAI was the undefined legal status of Native Americans. Prior to the 1924 Indian Citizenship Act, indigenous peoples were not considered citizens, and the birthright citizenship of the 14th amendment specifically excluded Native Americans. Since they were not citizens, Native Americans were subject to conflicting local, state, and federal laws that influenced everything from taxation to voting rights. The SAI believed citizenship would provide a way to codify indigenous rights, reduce government control over indigenous lives, and allow for greater self-determination. In one of the first acts the SAI lobbied Congress to establish an Indian Code Commission to codify existing federal law regarding the legals status of indigenous peoples.

At the time the SAI faced tremendous backlash, not only from white citizens, but also from other indigenous peoples who disagreed with the routes taken by the SAI. Fierce debates pitted those who advocated for birthright citizens against those who sought a gradual path to citizenship, like the paths in place for immigrants. Other indigenous leaders, knowing full well the U.S. rarely gave anything to indigenous peoples without demanding something in return, feared the establishment of citizenship rights would be met with the removal of treaty rights and reduction in tribal sovereignty. Balancing these demands, the SAI fought for citizenship while refusing to surrender any legal rights inherent in the >150 treaties agreed upon with the U.S. government, and without surrendering membership to an individual's Indian nation.

The SAI brought national attention to other issues, like the paternalistic role of the Office of Indian Affairs, whose incompetence resulted in abhorrent conditions throughout Indian Country. SAI members tirelessly demanded inquiries into terrible living conditions on reservations. They brought the evidence of poverty, unemployment, high infant mortality rates, disease, and continual erosion of indigenous land rights to a national audience. Their efforts, in part, would finally lead to an extensive survey of conditions in the Indian boarding school system. The Meriam Report, published in 1928, laid bare the abysmal conditions at residential schools throughout the country. As a brief example of these terrible conditions, the Meriam Report found the average per capita food allowance in government schools amounted to 11 cents a day. For reference, the report indicated a reasonable food allowance required at least 35 cents per student. Every boarding school surveyed in the report fell below that standard.

Eventually, disagreements between factions within the SAI resulted in it's dissolution by 1923. In it's brief history of the SAI established a firm foundation that future indigenous civil rights efforts could build upon; the demand for self-determination, citizenship without relinquishing tribal affiliation, the right to adequate education, and reform of abysmal conditions throughout Indian Country. In addition to Maroukis's We Are Not a Vanishing People, I also highly recommend Lewandowski's Red Bird, Red Power: The Life and Legacy of Zitkala-Ša for a very engaging look at one of the most influential indigenous activists of the era.