Dr. William Worrall Mayo arrived in Rochester from nearby Le Sueur, Minn., in 1863, during the Civil War. In 1861, Dr. Mayo had volunteered for duty in the Union forces. Because his application as regimental surgeon was denied, he began looking for other ways to serve the Northern cause.
When the federal conscription act was passed in 1862, Minnesota was divided into two districts with an enrollment board in each to select recruits. Dr. Mayo secured the examining surgeon position on the board that covered the southern half of the state. In May 1863, he reported for duty at the board's new headquarters in Rochester.
He immediately liked the vitality of Rochester, with the railroad at its doorstep. By January 1864, he had bought property and moved his family from Le Sueur. It would be the last and most successful change of residence for the founder of the famous medical family. Dr. Mayo was approximately 44 years old when he settled in Rochester.