The entrance to Mercyhurst's eighty-five-acre campus in the southern part of the city is dramatically highlighted by the elaborate twenty-foot iron gates designed in England and constructed in France for Harry K. Thaw, who murdered architect Stanford White in 1906. When Thaw's Pittsburgh estate was sold in 1950, Mercyhurst's founder, Mother Borgia Egan of the Sisters of Mercy, bought the gates for $600, on the advice of architect Brandon Smith, who then designed their installation in Erie.
Mercyhurst was founded in 1926 as a women's college, and men were admitted in 1969. The campus is dominated by its original building, Old Main, designed in 1925–1926 by Philadelphia architect Francis Ferdinand Durang, in a Collegiate Gothic style in golden brick with limestone trim. A massive, square, four-story entrance pavilion and sloping slate roof distinguish the design. The roof is punctuated by elongated dormers, which emerge from large pilasters on the floors below. In 1953, Brandon Smith designed the adjacent Weber Memorial Hall and connected the two with a cloister. Smith continued the Gothic Revival theme often favored for colleges.
Of the nearly sixty buildings on campus, those constructed in the 1950s, such as McCauley Hall (1959), are simple rectangular brick boxes. Two buildings by Francis Pisani and Jack P. Falco of New York City in the 1970s, including Baldwin Hall, initially used color to enliven their design, but both have been substantially altered from their original appearance. And several buildings have been altered to blend with Old Main and Weber Hall by the addition of extra stories and gabled roofs designed by the architectural firm Weibel, Rydzewski and Schuster. In 1997, the golden brick Hammermill Library, updated by Rectenwald Buehler of Erie, took center stage on the campus just inside the wroughtiron gates. The Audrey Hirt Academic Center (2002, Weber Murphy Fox), a two-story H-shaped brick classroom building, is crowned by a copper-clad dome.