Thomas Clark Callister, Jr. was born on May 1, 1881, in Fillmore, Utah, the son of Thomas Clark Callister, Sr. and Alice Melissa McBride Callister. Clark, as he was called, had deep family roots in the community; his grandfather was one of the first LDS bishops in Fillmore, and his father, who also served as bishop, worked as the county clerk, recorder, probate judge, and county superintendent for the schools of Millard County. In 1903 Clark graduated with a Bachelor of Science in Civil Engineering from the Utah Agricultural College in Logan and accepted a job with the United States Reclamation Service before returning to Fillmore in 1906. There Clark married Millie Peterson and worked for several irrigation companies in Millard County, including the Sevier River Land and Water Company. He spearheaded the organization of the Pahvant irrigation district in 1917, which was responsible for the irrigation of thirty thousand acres in the vicinity of Fillmore and Holden.

In 1903, the Western Union Telegraph Company decided to discontinue service over the Deseret telegraph line, which served much of southern Utah, including Millard and Juab Counties. Clark, with the help of his father, purchased the line and continued operating it, often at a loss in an effort to maintain telegraph communication in these areas. He served as manager of the company, the Millard County Telegraph and Telephone Company, as well as the manager and director of the People's Telephone Company. Clark also served two terms as the mayor of Fillmore from 1917 to 1920. Among his accomplishments were the construction of the town's first sidewalks, the installation of its first electric light system, and expansion of its waterworks. A resident of Fillmore for almost all of his life, Clark died there on August 31, 1967.