[3] Mahan was selected as a first-team All-American in each of those years, leading Harvard to a three-year record of 24–1–2.

[4] Mahan played his first varsity game for Harvard in 1913 against Maine and scored two touchdowns, including a 67-yard run.

[5] As a senior and team captain in 1915, Mahan climaxed his college football career by scoring four touchdowns and kicking five extra points in a 41–0 win over Yale, the worst defeat in Yale's 44 years of college football to that time.

Haughton reportedly responded, "Mahan, you are the greatest football player God ever made.

When Jim Thorpe was asked to choose the greatest football player of all time, he selected Mahan.

In 1927, George Trevor of the New York Sun selected an all-time backfield made up of Mahan, Walter Eckersall, Jim Thorpe, and Willie Heston of Michigan.

"[5] In 1951, Mahan was inducted into the College Football Hall of Fame as part of the first group of inductees.

Mahan described his negotiations in an interview with the Oakland Tribune:"I had a chance first to go with the Boston Red Sox when I was in my senior year at Harvard.

I considered the Braves more seriously than any other team but my negotiations there too were not satisfactory ..."[1]Mahan received a Bachelor of Arts degree from Harvard in the spring of 1916, with a major in political science and economy.

[1] He played semi-professional baseball in New Haven during the summer of 1916 and also worked as the head of the Woodrow Wilson clubs in New York state.

[12] At the end of the war, Mahan remained in Europe for a time working for Herbert Hoover's Food Administration.

A press account reported that Mahan was the star of the game, running 65 yards for the first touchdown:"In spite of the muddy field, speed and generalship on the part of the S.O.S.

He grabbed a short punt …, eluded two men who barred his path, shook off a third tackler further down the field, and sprinted 65 yards for a touchdown.

[15] He made his debut in investment banking in August 1927, accepting a position with the Wall Street firm Hornblower & Weeks.

[17][18] In 1975, after a long illness, Mahan died of cancer at Glover Memorial Hospital in Needham, Massachusetts.