Ponca Indians, a tribe of the Siouan linguistic family. They were closely associated with the Omahas and in the early 1800's settled with them in northeastern Nebraska. The Poncas were forcibly removed to Indian Territory (Oklahoma) in 1877–78. When some returned to Nebraska, they were arrested. Their trial resulted in a landmark decision holding that an Indian was a person within the meaning of the Constitution and entitled to full protection of the law.