The Andover-Newton Theological Seminary occupies a campus on a small hill directly above Newton Center. Established by the First Baptist Church of Boston in 1826, the Newton Theological Seminary developed a long affiliation with the Andover Seminary in Andover, Massachusetts, with which it merged in 1931. Newton Center resident Gardner Colby donated the funds for the library and chapel named in his honor. Esty's design for Colby Hall (NR/NRD) is appropriately austere for a Baptist theological school. Constructed of stone to prevent destruction by fire, the building has an atypical third-story mansard roof, which is almost vertical and built out to the cornice. At one side rises a four-story tower with a conical roof that, given the building's hilltop site, would have been highly visible to travelers on the Boston & Albany Railroad below. In 1897 Kendall, Taylor and Stevens designed the small stone Gothic chapel attached to the other side of Colby Hall.
Behind Colby Hall lies a quadrangle with a range of buildings dating from before the unification of the two schools: Farwell Hall (NRD), the first building, constructed in 1828 and enlarged with an additional story and a mansard roof in 1857; Sturdevant Hall (NRD) in 1873; and the Hill Library in 1895 by Kendall, Taylor and Stevens. Most of the other structures post-date the 1931 merger. Along the entrance road the school built several Mansard- and Queen Anne–style buildings.