Galena is the largest city in Jo Daviess County, Illinois, United States, and its county seat. It had a population of 3,308 at the 2020 census. A 581-acre (235 ha) section of the city is listed on the National Register of Historic Places as the Galena Historic District. The city is named for the mineral galena, which was in the ore that formed the basis for the region's early lead mining economy.