Immediately following his graduation in 1875, Ricketts was appointed as Assistant in Mathematics and Astronomy at RPI. During his first year in that role, he was invited to become an alumni member of Theta Xi (a fraternity founded at RPI in 1864). Ricketts was promoted to Assistant Professor in 1882 and became the William H. Hart Professor of Rational & Technical Mechanics in 1884 (the first endowed chair established at Rensselaer). Ricketts was described as "one of the most popular instructors in the Institute, a man whom we have honored for years, and whom we expect to see bringing great credit to his Alma Mater in his present position." [The Polytechnic, May 13, 1885]