Born in Nampa, Idaho, Horton lived in Lewiston as a youth and later in Boise. He graduated from Borah High School in Boise in 1977. He attended the University of Washington in Seattle and received a Bachelor of Arts in political science in 1982.
Horton then attended the University of Idaho in Moscow and received his Juris Doctor from its College of Law in 1985. Horton was appointed by Governor Butch Otter in September 2007 to fill the vacancy of the retiring Linda Copple Trout. He narrowly retained his seat in the statewide election in May 2008, but was re-elected by a wide margin six years later in 2014.
