He married Adaliza Keene of Lexington, Kentucky, on November 7, 1823, and they had 13 children.

He moved to Covington, Kenton County, Kentucky, studied law and was admitted to the bar in 1821 and commenced practice in Lexington.

Services were held at the Masonic Hall in Covington and burial was in the Southgate vault in Linden Grove Cemetery.

The Licking Valley Register (a local newspaper) said Southgate's unexpected death had "cast a gloom over the city such as we have never before witnessed".

This article incorporates public domain material from the Biographical Directory of the United States Congress