"Philosophical Hall, located at 104 South Fifth Street, between "Chestnut and "Walnut Streets, immediately south of "Old City Hall, was built in 1785–89 to house the society and was designed by Samuel Vaughan in the "Federal style. A third floor was added in 1890, to accommodate the expanding library, but was removed in 1948–50 when the building was restored to its original appearance for the creation of "Independence National Historical Park. In 2001, it was opened to the public as The American Philosophical Society Museum, hosting revolving, thematic exhibitions that explore the intersections of history, art, and science. The museum features works of art, scientific instruments, original manuscripts, rare books, natural history specimens, and curiosities of all kinds from the APS's own collections, along with objects on loan from other institutions.
In 1789–90, the "Library Company of Philadelphia (LCP) built its headquarters directly across 5th Street from APS. LCP sold its building in 1884, which was demolished for the expansion of the Drexel & Company Building in 1887. This building itself was demolished in the mid-1950s, during the creation of Independence National Historical Park.
APS built a library on the site in 1958, and recreated the facade of the old LCP building.
APS restored the former Farmers' & Mechanics' Bank building at 425–29 Chestnut Street, which was built in 1854–5 to the design of John M. Gries in the "Italianate style, to serve as a lecture hall. It is the site of meetings and most major events hosted or produced by the society.
"Constance C. and Edgar P. Richardson Hall at 431 Chestnut Street, immediately west of Benjamin Franklin Hall, is the former Pennsylvania Company for Insurances on Lives and Granting Annuities Building, which was built in 1871–73 and was designed by "Addison Hutton. It now contains offices and the Philadelphia Area Center for History of Science.
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