[7][8] In 1925, after graduating from Los Angeles High School, Cary entered the California Institute of Technology.

He held a variety of engineering and accounting positions with the company during the early years of the Great Depression.

[12]: 140  Cary distinguished himself in work relating to pH meters and glass electrodes, and became vice-president of development.

[13] Cary made substantial contributions, including the design of a reliable ultraviolet phototube for the instrument.

[12]: 164  The DU spectrophotometer was the first easy-to-use single instrument containing both the optical and electronic components needed for ultraviolet-absorption spectrophotometry.

[12]: 153–154 During World War II, National Technical Laboratories worked on a number of then-secret projects, including one for the development of synthetic rubber.

The Office of Rubber Reserve of the United States government contracted with NTL to produce an infrared spectrophotometer based on a single-beam design by Robert Brattain of Shell Development Company.

The Applied Physics Corporation made its first delivery, a Cary 11 UV-Vis spectrophotometer, to Mellon Institute in Pittsburgh, Pennsylvania, in April 1947.

Appearing on the market in 1954, it was the first commercial UV-VIS-NIR instrument to fully extend into the near-infrared spectrum.

[31][32] Cary was honored for: "his painstakingly careful and very valuable contributions to the design and production of highly precise instrumentation in areas which range from spectroscopy to chemical, medical and nuclear research.

"[33] In 1977, Howard Cary received the Maurice F. Hasler Award[34] at Pittcon "for his pioneering leadership in the development of instrumentation for absorption and Raman spectroscopy".