Measuring 125 feet long and 25 feet wide, the building featured gray stone walls offset by red brick quoins. Seen for the first time on the campus in Reunion Hall, this deliberate contrasting of color was a notable characteristic of other High Victorian Gothic structures built in the McCosh era.

Located between West College and Geological Hall, Reunion Hall was built on the former location of the Joseph Henry House, which was moved to the eastern side of the campus. Deliberately off-line in its placement, Reunion negated the symmetrical plan for the College envisaged by Joseph Henry in the 1830s.

For students, Reunion was problematic from the beginning. Lit by gas and heated by steam, these systems were intended to improve on the old kerosene lanterns and coal fires of the other dormitories. But the steam heat proved unreliable, causing residents much misery. And then there was the political geography. Advising students to shun the new dormitory, one undergraduate wrote in 1871, "Every bit of fun you have [in Reunion] will be distinctly audible at the President's House."