 McElwee graduated from Haddonfield Memorial High School, where he was a three sport letterman, and a 1957 graduate of the United States Naval Academy, where he played linebacker for the football team and was a member of the Sugar Bowl championship team in 1955.Following graduation, McElwee was commissioned in the United States Air Force serving as a pilot and utilities engineer.McElwee began officiating in 1961 while stationed at Hamilton Air Force Base in California.