He is an enrolled member of the Cherokee Nation of Oklahoma and served as Principal Chief from 1975-1985 when he resigned to accept the position of Assistant Secretary - Indian Affairs with the Bureau of Indian Affairs, a bureau within the U.S. Department of the Interior. Wilma Mankiller, Deputy Chief of the Cherokee Nation succeeded Swimmer as Chief of the Cherokees.
A member of the Cherokee Nation, Swimmer served as president of the Cherokee Group, L.L.C., from 1995 until 2001. The Group is a consulting firm that represents Indian clients engaged in government issues at the state and federal level, and supports the development of businesses on Indian lands. He was also Of Counsel to the Tulsa, Oklahoma, based law firm of Hall Estill, where his wife Margaret is a Partner.
On November 26, 2001, he became Director of the Office of Indian Trust Transition, which is a Department of Interior office that is attempting to bring the Indian Trust accounting process up to minimum court-ordered standards (Cobell v. Kempthorne).