Clarence Howard Johnston Sr. (August 26, 1859 – December 29, 1936) was an American architect who practiced in the state of Minnesota during the late 1800s and early 1900s. His work specialized in domestic, religious, and public architecture.
Johnston's parents, Alexander Johnston and Louise Johnston (née Buckhout), moved to Waseca County, Minnesota, in 1856, along with a few other families. They established a settlement named Okaman on the shores of Lake Elysian. Their first son, John Buckhout Johnston, was born in 1858, and became a prominent manufacturer and businessman. Clarence Johnston was born August 26, 1859. The family then moved to Wilton, which was then the county seat of Waseca County, and Alexander Johnston took over the publication of a local newspaper. In 1861 the family moved to Faribault. Their third child, Grace, was born March 2, 1862. They moved again, to Saint Paul, where their fourth child, Charles Albert, was born in 1864. After moving briefly to Hastings, the family returned to Saint Paul permanently in 1868. Alexander Johnston was then a reporter for the Saint Paul Daily Pioneer, now the Pioneer Press.
Johnston started attending Saint Paul High School in 1872 and took on a job as a clerk at the law firm of Rogers and Rogers. His mother died May 8, 1874, at the age of forty-two. That same year, Johnston quit his clerical job and began work at the firm of Abraham M. Radcliffe as a draughtsman. Radcliffe's firm was a local training ground for aspiring architects at the time. In September 1876, Cass Gilbert joined Radcliffe's firm as an apprentice, and Gilbert and Johnston soon became close friends. In the fall of 1878, Gilbert and Johnston enrolled at the Massachusetts Institute of Technology (MIT). There they met James Knox Taylor, who had also grown up in Saint Paul and joined MIT as an architectural student a year earlier. Gilbert and Johnston, along with Taylor, had opted to take the special two-year course in architecture, rather than the full four-year degree-granting program. However, Johnston was forced to drop out after one term due to financial reasons. He moved back to Saint Paul and worked briefly at the firm of Edward Bassford, where the firm was more conscious of costs to the client in the design and construction process. This influenced Johnston to view economic constraints as a challenge to be solved by inventiveness, instead of being a restriction on his artistry. During these years, Gilbert and Johnston kept in touch through a large number of letters.