Mullin's father, Jim, said he never doubted his son would win the district once he announced his candidacy last year.
“Everything he's started, he's accomplished,” Jim Mullin said. “And he's never started even. He's always started behind.”
Mullin will be the first Republican to represent the district, which is heavily Democratic in registration, in its current configuration. Rep. Dan Boren, D-Muskogee, who represented the district from 2005 until this week, did not run for another term.
Jim Mullin said he thinks one of his son's accomplishments will be negotiating with members of the other party.
Rep. Tom Cole, R-Moore, said Mullin's election doubled the number of American Indians in Congress. Cole is a Chickasaw. Mullin is a member of the Cherokee Nation.
Cherokee Nation Principal Chief Bill John Baker presented Mullin with a tribal blanket at Thursday's reception, and Cherokee Council member Jack Bauer read a resolution honoring Mullin's election to Congress.
“I know that Markwayne has the ability and the fortitude to make us extremely proud,” Bill John Baker said. “His mother never thought that he would be in Congress. She thought he might be president some day.”
Cole, who has been in Congress since 2003, was also sworn in Thursday for a new term, as were Lankford, an Oklahoma City Republican who has been in the House since 2011, and Rep. Frank Lucas, R-Cheyenne, who won his first term in 1994.