In 1988, the Pierpont Morgan Library bought 231 Madison Avenue from the Lutheran Church. The garden between the house and the main building's annex was redeveloped with a glass conservatory designed by Voorsanger and Mills. The conservatory, the first major expansion to the Pierpont Morgan Library since the completion of Morris's annex, was finished in 1991 and connected the two structures. The house became the Pierpont Morgan Library's bookstore. In 1999, the Morgan opened a drawing center on the second floor of the annex, designed by Beyer Blinder Belle. The same year, the Morgan received $10 million from Eugene V. Thaw and Clare E. Thaw; these funds were used to establish the Thaw Conservation Center in 2002.