The Mercer Museum is home to the Bucks County Historical Society and the Spruance Library; 84 South Pine St, Doylestown PA 18901; phone: 215-345-0210. Built in 1916, the museum is a National Historic Landmark. It is essentially a museum of pre-industrial American tools, trades and crafts.
The Museum (along with Fonthill and the Moravian Pottery and Tile Works) were entered onto the National Register of Historic Places separately in the 1970s, and collectively, as a National Historic Landmark, in 1984. Text, below, is excerpted from a copy of the original 1984 nomination document. 
Mercer's pursuit of archeology and anthropology led to his interest in pre-industrial tools and artifacts. His collection of "Tools of the Nation Maker" is the most comprehensive of its type in the world. The large museum, constructed of concrete, from the inside out, stands on the grounds of the Bucks County Historical Society. There were no plans or drawings; workmen just followed his directions. One of the first buildings totally constructed in reinforced concrete, the museum, although larger than his house (Fonthill) resembles it in form and detail.
The building has a medieval flavor, with towers, chimney dove cotes, turrets, etc. All floors housing this remarkable collection are of concrete, as well as the windows and roof. The museum is 115 feet high and is 97 feet by 71 feet. It contains 297 windows varying from 1 1/2 feet square to 10 to 15 feet square with rounded heads. The interior is an open well from floor to ceiling with a ramp that begins at ground level and leads to a balcony that runs continuously past 40 alcoves filled with tools of forty crafts and trades. There are over 30,000 artifacts including hand tools and machines. The building was dedicated on June 17, 1916.
The other buildings on this site are a new-Georgian building designed for the Bucks County Historical Society by Horace Trumbauer in 1904. In addition, there is a furnished log cabin originally build in Doylestown (circa 1799) and moved to the museum site in 1911. Two carriage sheds originally at the Abington Friends Meeting were re-installed in 1969 and now house a carriage collection: the newest addition to the complex is the Library wing, designed by A. Oscar Martin in 1933-1936 to complement Mercer's original concrete structure.