[5] Deuel County lies on the east boundary line of South Dakota.

The county's highest elevation occurs on its upper west boundary line, at 1,936 ft (590 m) ASL.

It was strongly Republican in its early years, with no Democrat except William Jennings Bryan gaining forty percent up to 1928.

Franklin D. Roosevelt in 1932 became the first Democrat to carry the county, but lost it to Alf Landon in 1936, whilst – like most of the Midwest – the county showed a powerful anti-Roosevelt trend in 1940 and 1944 due to opposition to World War II.

From 1964, the county showed a strong trend towards the Democratic Party – so much so that it was one of only 130 counties nationwide to support South Dakota native George McGovern in 1972 against Richard Nixon, and one of only five nationwide to have supported both landslide losers Landon and McGovern.

Over the past three elections, however, Deuel – in common with many rural counties nationwide – has shown an abrupt swing towards the Republican Party.