Farmington is a city in and the county seat of St. Francois, Missouri, United States. It is in the Lead Belt region in Missouri. As of the 2020 census, the population was 18,217. Farmington was established in 1822 as Murphy's Settlement, named for William Murphy of Kentucky, who first visited the site in 1798. When St. Francois County was organized, the town was briefly called St. Francois Court House and later renamed to Farmington.