South Dakota was admitted to the Union on November 2, 1889, and elects U.S. senators to class 2 and class 3. Its current U.S. senators are Republicans John Thune (since 2005) and Mike Rounds (since 2015). Karl E. Mundt is South Dakota's longest-serving senator (1948–1973). South Dakota is one of fifteen states alongside Arizona, Colorado, Florida, Georgia, Hawaii, Idaho, Indiana, Louisiana, Maine, Massachusetts, Minnesota, Missouri, Nevada and Utah to have a younger senior senator and an older junior senator. South Dakota's class 3 seat also holds the distinction of having a future Senate Majority Leader (John Thune) defeat and succeed a former Majority Leader (Tom Daschle).

List of senators

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