Born in Dresden, Tennessee, Slemons attended Bethel College. He moved to Arkansas in 1852. He studied law. He was admitted to the bar in 1855 and practiced in Monticello, Drew County. He served as member of the Arkansas State convention in 1861. He entered the Confederate States Army in July 1861 and served as colonel in Price's Cavalry throughout the Civil War. He resumed the practice of law. He served as district attorney 1866-1868.