In 1919 he returned to Salt Lake City, where he formed a partnership with architect Francis D. Rutherford. In 1920 Rutherford left for California, and Ashton continued the practice on his own. In 1923 he formed a new partnership with Raymond Evans, known as Ashton & Evans."Ashton, Raymond Joy" in American Architects Directory (New York: R. R. Bowker Company, 1962): 22.R. Randall Vosbeck, A Legacy of Leadership: The Presidents of the American Institute of Architects, 1857–2007 (Washington: American Institute of Architects, 2008) With the addition of Bernis Eugene Brazier in 1946 the firm became Ashton, Evans & Brazier."Brazier, Bernis Eugene" in American Architects Directory (New York: R. R. Bowker, 1956): 61. The firm became Ashton, Evans, Brazier & Associates in 1962 with the appointment of Frederick Montmorency as partner and Ashton, Brazier, Montmorency & Associates in 1963 after Raymond Evans' death. After Ashton's retirement in 1970 the firm became Brazier, Montmorency, Hayes & Talbot, with Brazier at the head of the firm."Montmorency, Frederick" in American Architects Directory (New York: R. R. Bowker, 1970): 635. Brazier died shortly afterward, after which Montmorency assumed control. The firm is still in business today (2022) as MHTN Architects.
