Returning to the field of education, he became principal of the Albany Academy in 1848, and in 1851, he assumed the position of professor of oriental languages in the theological seminary in New Brunswick. While in this position, he filled, gratuitously, the professor of belles lettres in Rutgers College during a period of 12 years. In 1862, Campbell was appointed president of Rutgers College.
Rutgers College transformed considerably during Campbell’s presidency. The changes were reflected in the students, the curriculum, the faculty, and the institutional structure of the college. In 1864 Rutgers gained further independence from the Reformed Dutch Church when the general church synod reconveyed Old Queens and campus to the college and withdrew its faculty from its teaching responsibility. The Rutgers Scientific School, established in 1862 with the assistance of professor George H. Cook, was designated by the legislature as the land-grant college for New Jersey in 1864 under the Morrill Act. The land-grant status brought Rutgers into a relationship with the State of New Jersey for the first time in its history. President Campbell and the trustees completed the “New Endowment Fund” by raising over $137,000. They also assembled a strong and assertive faculty, individuals who differed significantly from their predecessors in background, scholarly achievement, and approach to knowledge. In 1872 construction was completed on Geological Hall, erected between Old Queens and Van Nest Hall, which housed an armory in the basement, laboratories for the physical sciences on the first floor, and a large museum on the second floor. In the same year the college received the residuary estate of Sophia Astley Kirkpatrick, in the amount of $65,000, which was used to construct the chapel that bears her name. The structure, which also contained a library, was dedicated in December 1873.