The Signet Library building, begun in 1810 to a design by Robert Reid, with principal interiors by William Stark, originally comprised a Lower Library for the Society, completed in 1815, and an Upper Library for the Faculty of Advocates, completed in 1822, in time for the famous visit of King George IV to Edinburgh. Shortly thereafter, however, the Faculty decided to build a new library immediately to the south of, and parallel to, the Signet Library, and to meet the cost of its construction it was agreed in 1826 that the Upper Library should be sold to the Society for twelve thousand pounds. The entrance hall and stair, originally by Reid, had been reconstructed for the Faculty in 1819 by William Playfair and they were reconstructed for the Society in 1833 by William Burn so as to link the Upper and Lower Libraries for the first time. Many of the Society's portraits, including two handsome Raeburns and Sir John Watson Gordon's magnificent portrait of Lord President Hope, hang on this stair.
The furniture, made for the Faculty by William Trotter, the celebrated Edinburgh furniture maker, was sold by the Faculty to the Society in 1833 for the sum of three hundred pounds. Each piece was provided with a slip cover of brown glazed linen, and some of these are shown in use in Thomas Shepherd's well known view of the Upper Library, published as an engraving in 1831.
In the Upper Library, the cupola painting, by Thomas Stothard, depicts Apollo and the Muses, accompanied by the following poets, orators, historians and philosophers: Burns, Shakespeare, Homer, Milton, Virgil, Cicero, Demosthenes, Herodotus, Livy, Hume, Robertson, Gibbon, Newton, Bacon, Napier and Adam Smith.
The Garnkirk Urn, which stands at the west end of the room, was made by the Garnkirk Coal Company in Lanarkshire and given to the Society in 1842 by Thomas Sprot who was both a director of the company and a member of the Society.
The gallery originally ran across the west end of the Upper Library, but it was removed in 1868, apparently to improve "the appearance and lighting of the room". The original window was replaced with the present stained glass window to commemorate Queen Victoria's Golden Jubilee in 1887. It depicts, along with the Royal Arms and those of the Society, those of the Keepers and Deputy Keepers who had held office during the previous fifty years.