Library Hall Phildelphia ( side view)   Library Hall, at 105 South 5th Street is a 1959 reconstruction of the 1790 building originally built for the Library Company of Philadelphia. It is now occupied by the library of the American Philosophical Society. Founded by Benjamin Franklin in 1743, the Philosophical Society's library contains an unrivaled collection of Franklin's books and papers as well as those of other great scientists from then until now. Built: 1789 Reconstructed: 1954 Original architect: William Thornton WHAT'S INSIDE: The original journals of the Lewis and Clark expedition, A copy of the Declaration of Independence in Jefferson's own handwriting, A first edition of Sir Isaac Newton's Principia, A first edition of Charles Darwin's Origin of Species