He was named emeritus professor of physics at the University of Iowa and was awarded the Oersted Medal in 1943.

During the following year he worked at a Methodist Book Concern in St. Louis in order to pay for college.

[3] After receiving a loan to pay for his education, he entered graduate studies at the Cornell University in 1898.

Stewart was elected to Sigma Xi in 1900 and awarded his doctorate in 1901 with a thesis titled, The Distribution of Energy in the Spectrum of the Acetylene Flame.

[4] In 1903, assistant professor Stewart became chair of the small physics department at the University of North Dakota, succeeding C. J. Rollefson.

[4] When the USA entered World War I in 1917, Stewart was tasked by the National Research Council to develop a method for locating and tracking aircraft.

However, this study never made it out of the experimental stage, as the military turned to the French for their aircraft sound locator.

[9] Stewart was named acting dean of the graduate college during 1921–1922, in place of Carl E. Seashore who was on leave to Washington D.C.[10][11] In 1923, he had a university textbook published on the subject of acoustics.

[4] After 35 years as head of the University of Iowa physics department, in February 1946 he gave up the chair and was named professor emeritus.

[10] While at Iowa, he had played a role in founding the university's interreligious School of Religion and remained on its board for 25 years.