Once in Indian Territory (present-day Oklahoma), the Five Civilized Tribes worked to rebuild their economies. Most individuals focused on farming, with some providing other services such as blacksmithing. Economic revitalization was very successful, but it was later interrupted by the Civil War. Surrounded by states committed to the war, Indian Territory became a crossroads of conflict. Many residents suffered at the hands of the Union and Confederate armies; people were assaulted, farms and outbuildings burned, and crops and livestock stolen, destroyed, or dispersed. After the war, the tribes worked to rebuild their communities yet again. The United States, having allowed indigenous owners to retain slaves during removal, now insisted that all former slaves be freed and recognized as official members of the tribes of their owners; known as freedmen, this population experienced various phases of acceptance and rejection from others in the Native American community, and their status remained controversial in the early 21st century.

During Reconstruction (1865–77), conflicts in the West resulted in the movement of a large number of displaced Plains tribes and others from their traditional homelands to Indian Territory. The United States took land assigned to groups already resident in the territory and transferred it to the newcomers. By the 1890s, continued Euro-American land hunger had resulted in allotment, a federal policy under which land held in common by tribes was divided into parcels and dispersed. Each indigenous head of household was assigned a parcel, as were orphans and a few other categories of individuals. The remaining land was made available to settlers, railroads, and others for development. Although the Five Civilized Tribes were immune from the initial enforcement of the new policy because they held clear title to their property, an act of Congress brought them under allotment jurisdiction in 1898. Like the other indigenous residents of the territory, they lost tens of thousands of acres.

Under policies initiated in 1906, indigenous peoples lost the right to elect their own tribal governments, which were replaced by federally appointed chiefs and tribal councils. The administration of schools and other institutions formerly managed by the tribes of Indian Territory also devolved to the United States. With allotment, these policies paved the way for Euro-American settlement of the territory and thus for statehood. In 1907 Indian Territory and Oklahoma Territory combined to become the new state of Oklahoma.

These and other pressures on traditional culture were clear abrogations of tribal sovereignty, but tribes from the Southeast culture area saw just as clearly that fighting them head-on would prove unproductive. As a result, many engaged in passive resistance. Families refused to sign up for or receive their allotments; former tribal council members revitalized traditional governance and ritual activities away from the geographic seats of power; and children were schooled at home. Ironically, the United States’ efforts to complete the assimilation of the Southeastern peoples had resulted in a grassroots movement that strengthened traditional cultures considerably.

During the remainder of the 20th century, Southeastern peoples were affected by a number of events of global importance, such as the oil boom of the 1920s; the Great Depression; the World Wars and the Korean, Vietnam, and Gulf wars; and the advent of the civil rights and counterculture eras of the 1960s. In 1968 three Southeastern groups that had long been in bureaucratic limbo allied themselves to gain greater traction with the federal government. They included groups that had escaped removal—Cherokee communities in North Carolina and Seminole groups in Florida—as well as a tribelet of Choctaw that had traveled only as far as the state of Mississippi during removal. Having avoided removal and undertaken efforts to escape governmental scrutiny, they had seen many of their rights as native peoples abridged; their efforts eventually led to federal recognition of their status as tribes.

During the 1970s the federal government relinquished the right to appoint tribal governments; the Southeastern tribes quickly reinstated their constitutions and held elections. From that point into the early 21st century, the Southeast nations emphasized economic development, the revenues of which were used to support programs ranging from education to health care to cultural preservation. For instance, Chickasaw Nation Industries and Choctaw Management Services Enterprise, each owned by its constituent tribe, included firms providing construction, information technology services, and professional recruiting. The Florida Seminole instituted ecotourism programs that acquainted visitors with the state’s wetlands. Many tribes also turned to casino-based gaming (see Native American gaming); these operations often included hotel and restaurant facilities that generated income and provided employment to tribal members. Casino revenue, sometimes referred to as “the new buffalo,” lifted many tribes above the poverty line and encouraged a revival of traditional cultural practices.See also Native American: History; Native American: Developments in the late 20th and early 21st centuries.