Andover Hall is one of the staples of the Harvard Divinity School. The structure, designed by Allen and Collens, currently houses administrative offices, among a few other things, including a chapel. It is no wonder; the building is gorgeous. It makes sense that staff would want to have offices there. However, that is not how Andover Hall began in 1911.
Andover Theological Seminary was once an entity separate from Harvard Divinity School. This was also before it became the Andover Newton Theological School. However, enrollment was poor by 1906, so it was thought that a merger with Harvard would be best for the seminary school. This happened in 1908. By 1911, funded by $300,000 from the Andover Theological Seminary, Andover Hall opened. At the time, it housed dormitories, a library, lecture halls and a chapel.
While Collegiate-Gothic style architecture can be seen at Boston College, namely with the gorgeous Devlin Hall, and in other American institutions, Andover Hall is the only place in Harvard where it occurs. It is an impressive example and worth a look for even those not attending the divinity school. Harvard in general makes for good architecture spotting, so make the visit part of a longer outing.
As for the Andover Theological Seminary, it was not shut down by the lull in enrollment. It emerged stronger as the Andover Newton Theological School. As such, it is the United States' oldest theological graduate school still in existence. For more information about the Andover Newton Theological School, visit its official website.