Harmon Runnels was a Patriot captain in the Georgia Continental Line during the Revolutionary War. He came to the Mississippi Territory in 1810 and in 1811 purchased two land sections along the western bank of the Pearl River, the earliest land settled in what is now Lawrence County and the site where Monticello was established. Runnels platted and named the town in honor of President Thomas Jefferson's famous residence and donated lots for a market, public square, church, school, and cemetery. In the Mississippi Territory Assembly of 1813, he represented Marion and Hancock counties. After Lawrence County was formed by a division of Marion County at the Probate Court of December 22, 1814, Runnels became Chief Justice. He also served in the Mississippi Constitutional Convention of 1817 and in the Mississippi House of Representatives and Senate, serving thirty years total in the Georgia and Mississippi legislatures. Harmon Runnels died in Monticello at eighty and was buried in the City Cemetery. His son, Hiram George Runnels, was Governor of Mississippi in 1833, and his grandson, Hardin Richard Runnels, was Governor of Texas in 1857.