Preparation of P 25107, the holotype of Brachiosaurus, began in the fall of 1900 shortly after it was collected by Elmer Riggs for the Field Museum of Natural History (Chicago). As the preparation of each bone was finished, it was put on display in a glass case in Hall 35 of the Fine Arts Palace of the Worlds Columbian Exposition, Field Museum's first home. All the bones were on display by 1908 when Field Museum's newly mounted Apatosaurus was unveiled. However, no mount was attempted because only 20% of the skeleton had been recovered. In 1993, the holotype bones were molded and cast, and the missing bones were sculpted based on Giraffatitan material in Berlin. This plastic skeleton was mounted and, in 1994, put on display at the north end of Stanley Field Hall, the main exhibit hall of the Field Museum's current building. The real bones of the holotype were put on exhibit in two large glass cases at either end of the mounted cast. The mount stood until 1999, when it was moved to the B Concourse of United Airlines' Terminal One in O'Hare International Airport to make room for the museum's newly acquired T. rex, "SUE".[25] At the same time, the Field Museum mounted a second plastic cast of the skeleton (designed for outside use) and it has been on display outside the museum on the NW terrace ever since. The only real bones currently on display are the humerus and two dorsals in the Mesozoic Hall of the Field Museum's Evolving Planet exhibit.