Worthington is a city in and the county seat of Nobles County, Minnesota, United States. The population was 13,947 at the time of the 2020 cen…Worthington is a city in and the county seat of Nobles County, Minnesota, United States. The population was 13,947 at the time of the 2020 census. The first European likely to have visited the Nobles County area of southwestern Minnesota was French explorer Joseph Nicollet. Nicollet mapped the area between the Mississippi and Missouri Rivers in the 1830s. He called the region "Sisseton Country" in honor of the Sisseton band of Dakota Indians then living there. It was a rolling sea of wide open prairie grass that extended as far as the eye could see. One small lake in Sisseton Country was given the name "Lake Okabena" on Nicollet's map, "Okabena" being a Dakota word meaning "nesting place of the herons".