The 3rd Wisconsin Infantry Regiment was an infantry regiment that served in the Union Army during the American Civil War.

Charles Smith Hamilton was a career United States Army officer who served with distinction during the Mexican–American War. He also served as a Union Army general during the early part of the American Civil War. After the war, he was appointed U.S. marshal for the Eastern District of Wisconsin by President Ulysses S. Grant, and served as president of the University of Wisconsin Board of Regents.