In the early stages of the design process, J. Pierpont Morgan’s son-in-law Herbert Satterlee took the lead in communicating with McKim, passing on information gleaned from Junius S. Morgan II, Pierpont’s nephew and adviser.

Here, Satterlee made clear that the new building would house “a collection of rare volumes,” rather than a “reading library.” Estimating that Pierpont already held about ten thousand volumes, Satterlee instructed McKim to plan for growth and incorporate a librarian’s office.