An artillery officer in the U.S. Army Reserve, he was the first N.C. State alumnus to lead the institution and the first leader of the university to hold the title of Chancellor.

[2] Though he apparently enrolled initially as a textiles student, he changed his major to mechanical engineering by his sophomore year.

[7] He was appointed captain of his cadet company in the fall of 1908, and was commended for his drilling abilities at a competition held on 16 October.

After completing his bachelor's degree, Harrelson returned to N.C. State as an instructor of mathematics in the fall of 1909, teaching arithmetic, algebra, and plane and solid geometry,[13] subsequently becoming a professor.

In October 1915,[7] he was commissioned a first lieutenant in the 1st Company of the North Carolina National Guard Coast Artillery Corps.

[15] In August 1916, Harrelson was promoted to captain in the National Guard and was assigned command of the 1st Company, Coast Artillery, then stationed in Raleigh.

Harrelson was a member of the local engineering fraternity Alpha Sigma Epsilon which became a chapter of Theta Tau in 1924.

[23] On February 25, 1943, Harrelson was recalled to permanent active duty, becoming the first head of a major Southern college to be so assigned.

Harrelson then began speaking, but before he could finish his first sentence, he suddenly collapsed to the floor, knocking over the microphone as he fell.

He was rushed to Rex Hospital and placed under an oxygen tent, but was pronounced dead from a cerebral haemorrhage at 10:10 p.m.[25] Harrelson died at age 69.

NCSU Libraries Special Collections Research Center currently houses John William Harrelson's manuscript papers and university archives.