[4] Grant County lies on the east side of South Dakota.

[5] The highest point of the terrain is on the county's south boundary line, towards its southwest corner, at 2,014 ft (614 m) ASL.

[7] The lowest point in the state of South Dakota is located on Big Stone Lake at Big Stone City in Grant County, adjacent to Ortonville, Minnesota, where the lake flows into the Minnesota River.

In terms of ancestry, 49.9% were German, 16.8% were Norwegian, 8.9% were Irish, 6.7% were Swedish, 5.6% were English, and 5.2% were American.

School districts include:[16] Grant County voters have been reliably Republican for decades.

In only three national elections since 1948 has the county selected the Democratic Party candidate.