Marquand is notable as one of the foremost art historians and critics of his time, and helped to popularize and establish the field in elite college campuses.

[2] During the 1881–1882 academic year, Marquand built a mechanical logical machine that is still extant; he was inspired by related efforts of William S. Jevons in the UK.

He also served as the first director of the Princeton University Art Museum, a position he held until his 1922 retirement.

[9] His first volume of critical writing on the Della Robbia was the inaugural installment of the Princeton Monographs, appearing in 1912.

On June 18, 1896, he married Eleanor Cross in the Church of the Holy Communion in South Orange, New Jersey.

[1] Together, Eleanor and Allan were the parents of four children:[2] Marquand died at the Presbyterian Hospital in New York on September 24, 1924, and was buried at Princeton Cemetery.