Duffield Ashmead, Jr., was born in Philadelphia, the son of Duffield and Margaret Simons Ashmead. He graduated from the William Penn Charter School in 1902 and from the University of Pennsylvania in 1906, receiving his B.S. in Architecture. Ashmead also acquired extensive office training: six months with Daniel Adams, a stairbuilder, three months with Wilson Eyre, three months with Newman & Harris, three months with John T. Windrim, two months with William C. Hays, and a year with Herbert C. Wise. In July, 1905 he entered the office of Alexander Mackie Adams, where he remained until 1908 and executed at least one project (according to the Philadelphia Real Estate Record and Builders Guide) under the name of Ashmead & Adams. In 1908 he and Clarence DeArmond founded DeArmond & Ashmead, which changed its name to DeArmond, Ashmead & Bickley in 1911, when George H. Bickley, DeArmond's classmate from the University of Pennsylvania, joined the partners. Again, according to the Philadelphia Real Estate Record and Builders Guide, some projects were executed under the name Ashmead & Bickley in 1914 and later, in 1928.

In 1940 Ashmead became ill following the death of his wife and was hospitalized for considerable time. The firm had already been dealt a blow by Bickley's death in 1938; and with the onset of World War II, DeArmond dissolved the firm and became a member of the Army Corps of Engineeers. After the war Ashmead established a rather casual firm with his friend Roland Taylor Addis. These two shared office space and worked together on a few commissions but apparently never really considered themselves a partnership. This association began in 1948 and terminated with the death of Ashmead in 1952.

While at the University of Pennsylvania, Ashmead belonged to the Architectural Society and served as editor for The Record of the Class of 1906. He joined the T-Square Club in 1906, the Philadelphia Chapter of the AIA in 1922, and the national AIA in 1924. Additional memberships included the Art Club of Philadelphia, the Sons of the American Revolution, and the Merion Cricket Club.

Written by Sandra L. Tatman.