McPherson County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 2,411. Its county seat is Leola.

James Birdseye McPherson (/məkˈfərsən/) was a career United States Army officer who served as a general in the Union Army during the American Civil War. McPherson was on the general staff of Henry Halleck and later of Ulysses S. Grant and was with Grant at the Battle of Shiloh. He was killed at the Battle of Atlanta, facing the army of his old West Point classmate John Bell Hood, who paid a warm tribute to his character. He was the second-highest-ranking Union officer killed in action during the war.