Joplin is a city in Jasper and Newton counties in the southwestern corner of the U.S. state of Missouri. The bulk of the city is in Jasper County, while the southern portion is in Newton County. Joplin is the largest city located within both Jasper and Newton Counties – even though it is not the county seat of either county. With a population of 51,762 as of the 2020 census, Joplin is the 12th most-populous city in the state.