Henry B. Boynton was born in West Chicago, Illinois, in 1899 and grew up in Amelia County, Virginia. He graduated from Virginia Polytechnic Institute in 1921 with a B.S. in Agricultural Engineering and then again in 1923 with a B.S. in Civil Engineering. He then spent a year (1923-24) at the University of Illinois in Urbana taking architecture classes. He became a registered architect in Virginia in 1930 (he later registered in West Virginia, North Carolina, and Pennsylvania).

From 1924 to 1928, Boynton worked as a draftsman at Carneal & Johnston, Architects & Engineers, in Richmond, Virginia. In 1929 he worked as an associate with Louis Phillipe Smithey, Architect & Engineer, in Roanoke, Virginia. In 1935 he and Smithey became partners and formed Smithey & Boynton, Architects & Engineers, in Roanoke. Boynton became senior partner of the firm when Smithey retired in 1963.

Smithey & Boynton designed several structures over the years, including, in Roanoke, Christ Episcopal Church, the South Roanoke Fire Station, the Shenandoah Life Building, McClanaham Street Office Building, and the American Theater Building. The firm also designed Lane Stadium at Virginia Tech.

Associations with which Boynton was affiliated include the Virginia Chapter (later changed to the Virginia Society & Blue Ridge Chapter) of the American Institute of Architects from 1938 to his death. He served on the board of directors in 1952, 1953, and 1956, as vice-president in 1954, and president in 1955. He was a member of the State Registration Board for Architects, Professional Engineers, and Land Surveyors, as a Governor's appointee, from 1962-72 (President of the Board in 1967). He received a distinguished service award in 1980, and the Noland Award in 1989, both from the Virginia Society & Blue Ridge Chapter of the AIA.

Boynton served in the Army Corps of Engineers during World War II and completed his career as a colonel. He was a member of the Virginia Tech Alumni Board of Directors from 1969 to 1979 and Chair of its Annual Fund Committee from 1973 to 1979. He served on the Board of the VPI Educational Foundation, Inc., from 1978 to 1982. In 1976 Boynton recieved the Virginia Tech Alumni Distinguished Service.

Boynton died on September 13, 1991, at the age of 92, at his home in Roanoke.