 In 2006, state Representative Mac Sumner announced his resignation due to his lung cancer.On December 27, Gilliam was selected to replace Sumner as representative from the 18th district by the county commissioners of Marion and Clackamas counties.On January 8, 2007, Gilliam was sworn into the Oregon House of Representatives and was appointed to serve on the consumer protection, and the human services and women's wellness committee during the 2007–2009 legislative session.