South Dakota became the 40th state to join the Union on November 2, 1889, with
Arthur C. Mellette elected as the new state's first governor.
Named for John L. Pennington, Dakota Territory governor, Pennington County was formed in 1875.
Pennington's first county seat was at a mining camp called Sheridan located at a spot which is
now Sheridan Lake. Located in western South Dakota and forming the center portion of the Black Hills, Pennington County also reaches far into the Badlands. With its mining, logging, and ranching background, the County has a colorful history.