His father was a pioneer in Columbiana County, Ohio, where he cleared a tract of government land and occupied it as a homestead.

During the Civil War, McGowan served in the Fifth and Ninth Regiments, Michigan Volunteer Cavalry.

He went into campaigns in East Tennessee with General Ambrose Burnside, until he was forced to resign in 1864 for reasons of poor health.

McGowan returned to Coldwater, where he studied law, was admitted to the bar in 1867, and commenced practice.

In 1876, McGowan was elected as a Republican from Michigan's 3rd congressional district to the 45th United States Congress.