The median age in the Black Hills region varies from county to county. The two most populous counties, Pennington, and Meade, have median ages of 38.8 and 35.9, in line with the national median age of 37.5.

The county with the oldest population is Fall River, with a median age of 50.5 and 23.1 percent of its citizens over the age of 65. Shannon County has the youngest population with a median 23.5 and 45.5 percent of its population under the age of 21.