Alert Shmoopers will recall that the "Five Civilized Tribes"—the Choctaw, Cherokee, Chickasaw, Muscogee, and Seminole—were exempt from the Dawes Act. These tribes had originally lived in the southeastern U.S. but were removed to "Indian Territory," in present day Oklahoma, by the aptly named Indian Removal Act of 1830.

They were "civilized" because they'd adopted a lot of European customs and beliefs in the early days of the U.S. Many converted to Christianity and participated in the American economy. Some of them were so acculturated that they had Black slaves and built plantations just like southern whites.

The author of the Curtis Act, Kansas congressman Charles Curtis, was of mixed European-Native American ancestry. He thought the Act would better the lives of the tribes—the official name Congress gave it was "Act for the Protection of the People of Indian Territory"—
but by the time the Act got through Congress, he probably didn't recognize it.

The Curtis Act extended the provisions of the Dawes Act to the Five Civilized Tribes. It broke up their communal governments, abolished their courts, and made allotments of their lands. Between the Dawes and Curtis Acts, the tribes lost jurisdiction over about 90 million acres of their property. It left it to the U.S. government—via a Commission headed by none other than Henry Dawes—to decide who was and was not a tribal member. The Act basically finished what the Dawes Act started (source).

The reason for all this? The U.S. was getting ready to create the new state of Oklahoma by combining the Oklahoma Territory with the Indian territory that was designated before the Civil War. By effectively destroying the Native Americans' tribal governments and claims to the lands, the way was clear for admitting Oklahoma to the Union.

The Five Civilized Tribes in Indian Territory proposed creating a state of their own, but you can guess how well that went over in Washington. In 1907, Oklahoma became the 46th state of the Union (source).

OK.