Clarence Howard Johnston Sr. (August 26, 1859 – December 29, 1936) was an American architect who practiced in the US state of Minnesota during the late 1800s and early 1900s.

That same year, Johnston quit his clerical job and began work at the firm of Abraham M. Radcliffe as a draughtsman.

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.

In the summer of 1880, Cass Gilbert returned from Europe and settled in New York, working for the firm of McKim, Mead & White.

That same year Johnston, Gilbert, Bacon, Taylor, and William A. Bates founded the Sketch Club, which later became the Architectural League of New York.

[1]: 14–16 After finally traveling to Europe and the Asia Minor in February 1883, Johnston returned to the United States and established his own practice in Minnesota in 1886.

Retaining private commissions allowed him to operate his office continuously and receive a higher rate of return.

Johnston was also architect for the Board of Regents of the University of Minnesota and drew plans for all the new buildings constructed on campus during his tenure.

Taking charge of the Johnston firm upon his father's death, he went on to design Coffman Memorial Union and the old Bell Museum building at the University of Minnesota, among other projects.