Howell County is a county located in the southern portion of the U.S. state of Missouri. As of the 2010 census, the population was 40,400. The largest city and county seat is West Plains. The county was officially organized on March 2, 1851, and is named after Josiah Howell, a pioneer settler in the Howell Valley.Howell County comprises the West Plains, MO Micropolitan Statistical Area.