The historic City of Black Hawk is a Home Rule Municipality located in Gilpin County, Colorado, United States. The city population was 118 at U.S. Census 2000, making Black Hawk the least populous city in Colorado. The tiny city is a historic mining settlement founded in 1859 during the Pike's Peak Gold Rush. It is located adjacent to Central City, another historic mining settlement in Gregory Gulch. The two cities form the federally designated Central City/Black Hawk National Historic District. The area flourished during the mining boom of the late 19th century following the construction of mills and a railroad link to Golden. The town declined during the 20th century, but has been revived in recent years after the 1991 establishment of casino gambling following a statewide initiative in 1990.