He became principal of Allendale High School before attending Southern Baptist Theological Seminary in Louisville, Kentucky, then resumed teaching in Bamberg.

Clemson trustee and U. S. Senator Benjamin Tillman lived only 5 miles (8.0 km) from Johnston, and was interested in Hartzog's background in agriculture, military, engineering, as well as his experience in South Carolina's secondary schools.

Improvements were made to the drinking water supply and campus dairy, and Hartzog changed the academic calendar to move the long break from winter to summer.

[7] In 1900, engineering professor (and future university president) Walter Riggs, who had coached Clemson's first football team convinced Hartzog to allow the formation of an athletic booster club.

[8] In early 1902, a sophomore cadet was charged with taking a test tube from the chemistry lab's supply closet to his work station without the permission of professor Richard Brackett.

[11] In 1905 Governor Jeff Davis replaced Hartzog with his hand-picked candidate, John N. Tillman, in an effort to broaden his power before a run for the United States Senate.