[4] Perkins County lies on the north edge of South Dakota.

Shadehill Reservoir is a large impoundment on the Grand River in the county.

Perkins County terrain consists of semi-arid rolling hills, carved by drainage creeks, sparsely dedicated to agriculture.

[5] The terrain slopes to the east; its highest point is on its lower west boundary line, at 3,097 ft (944 m) ASL.

Perkins County came to media attention in 2009 when Stephen Von Worley calculated that it was the site of the "McFarthest Spot" — the point in the continental United States that is most distant from a McDonald's restaurant: 107 miles (172 km) as the crow flies and 145 miles (233 km) by car.

In terms of ancestry, 47.4% were German, 26.2% were Norwegian, 10.8% were English, 8.7% were Irish, 8.4% were Swedish, and 5.8% were American.

No Democratic presidential candidate has won Perkins County since Franklin D. Roosevelt did so during his 46-state landslide in 1936.