[3] It was named for the former governor of the Dakota Territory and Civil War general Edwin Stanton McCook.

[4][5] McCook County is part of the Sioux Falls, SD Metropolitan Statistical Area.

[6] The terrain slopes to the south and southwest; its highest point is near its northeast corner, at 1,798 ft (548 m) ASL.

In terms of ancestry, 61.5% were German, 12.8% were Irish, 11.1% were Norwegian, 7.4% were Swedish, 6.2% were Dutch, 5.2% were English, and 3.5% were American.

Although the county was one only 130 nationwide to support favorite son George McGovern in 1972, it has selected the Democratic nominee in only six other elections since South Dakota's statehood, and none since 1980.