William Henry Cassity was born to Edward Penale Cassity and Mary Ann Bowden on 14 March 1856 in St. Louis, Missouri. His family moved to Tooele, Utah Territory, in 1862. In 1877, Cassity married Margaret Evans, who died in 1880 following the birth of their first child. He then married Mary Ann Williams on 22 April 1882. They had six children. Cassity worked at Waterman Smelter, drove a stagecoach, clerked in a store, and was a truck gardener. He was also involved in civic affairs as city judge, city councilman, school trustee, and county statistician. From 1913 to the time of his death, he served in the bishopric of the Tooele North Ward. He died in Tooele on 18 March 1923.
 “William Henry Cassity,” in History of Tooele County (Salt Lake City: Daughters of Utah Pioneers, Tooele County, 1961), 436; “William Henry Cassity Dies at Home in Tooele,” Salt Lake Tribune, 20 Mar. 1923, 7; “W. H. Cassity Is Summoned,” Tooele (UT) Transcript, 23 Mar. 1923, 1; “William Henry Cassity,” FamilySearch (Person ID: KWC2-WJ5), accessed 20 Oct. 2020, https://www.familysearch.org/tree/person/details/KWC2-WJ5.