His father, Dr. John E. Harris, moved his family to Bloomington in 1876, where they settled on what would later be the Leonard Springs water works plant. Three years later, they moved to a stately home at 213 S. College Avenue. John G. Harris eventually moved to Oklahoma and went into politics, but would return to Bloomington sometime before 1910, when he was elected for the first time as mayor. He was elected again in in 1914 and 1922, and died in office.
His brother Charles was also an accomplished Bloomington doctor.