Simms is Osage, Cherokee and Creek Indian, has a proven track record of building profitable businesses. He is the son of Evelyn OnHand Pitts and is the grandson of Ralph OnHand (Wah-Tsa-Ah-Tah) of the Beaver Band. After his father died, Simms was raised by the late William Pitts, brother of former Chief Paul Pitts, as his own son and in the traditional ways of the Osage. Later being adopted into the Bear Clan and given his Osage name, Le-Ta-Xoh, by Mary Red Eagle.
He attended OSU for three years majoring in Business administration with a minor in psychology. He left OSU to serve in the US Army and earned his associates degree upon his return to Oklahoma.
Mark was elected to the Osage Nation Council in 1994, where he served as second speaker for the first two years and Speaker for the remaining four years of his term. He sat on the Financial Committee and worked on the Osage Nation’s budget.
In 2006 Mark was elected to the newly formed Legislative branch as Congressman where he served for six years which included the Economic Development Committee with oversight over the Nations seven Casinos. He was appointed the Osage Energy Services, LLC and now the Osage Nation Gaming Enterprise Board where he serves as Chair.
Other appointments and honors include 2003 – Business Man of the Year by Oklahoma Business Advisory Council and National Republican Congressional Committee; Appointed to President George W. Bush’s Business Commission where her served from 2001-2009; Honored in various editions of Who’s Who and is active in many professional and civic organizations. Simms received the prestigious Dr. Ralph Dru Career and Professional Award in 2013 from the Tulsa Area Indian Affairs Commission.