Clark volunteered for the Confederate forces in 1862 and saw action as an officer.

After the war Clark enrolled as an advanced student at Carlton College in Bonham. After graduation in January 1869, he married Sallie McQuigg. They had eight children.

Clark and his brother Randolph Clark moved to Fort Worth the same year and established a school there under the auspices of the local Disciples of Christ church.

In 1874 Clark moved to Thorp Spring where he, his brother, and their father opened a school they called Add-Ran College, after the first syllables of the brothers' first names. Addison was listed as president of the college from its opening in 1873, but he had remained in Fort Worth for a year to oversee the school there. Add-Ran Male and Female College, as it was officially called, also included a preparatory department. The school grew quickly, and in 1877 the Clarks built a larger facility across the road from the original building.

Costs of construction and high operating expenses proved to be too much, and in 1889 the Clarks gave the institution to the Christian Church (Disciples of Christ) of Texas. Addison Clark continued as president, and the name was changed first to Add-Ran Christian University and later to Texas Christian University, although Clark was opposed to both name changes. In 1895, against his wishes, the university was moved to Waco. Clark remained president until 1899 when he stepped down. He continued to teach ancient languages until 1904 when he resigned from the faculty.

Clark also held pastorates in Waco and Amarillo until 1904, when he became president of Add-Ran Jarvis College in Thorp Spring, which occupied the same buildings as the original Add-Ran before its move to Waco.

When Add-Ran Jarvis was forced to close in 1909, Clark moved to Mineral Wells to serve as pastor of the Disciples of Christ church. He died in Mineral Wells on May 12, 1911 and was buried in Thorp Spring.

BIBLIOGRAPHY: Joseph Lynn Clark, Thank God We Made It (Austin: University of Texas, 1969). Randolph Clark, Reminiscences (Wichita Falls: Lee Clark, 1919; rpt., Fort Worth: Texas Christian University Press, 1979). Jerome A. Moore, Texas Christian University: A Hundred Years of History (Fort Worth: Texas Christian University Press, 1974).