ABSTRACT In 1632, John Milton went to live with his parents outside of London and undertook a rigorous program of reading. Scholars have long wondered which, if any, institutional collections he might have consulted. This question offers the opportunity to bring attention to London’s first public library, where Milton may well have studied, in its earliest decades. Formed for the benefit of the London clergy, Sion College is shown to have welcomed readers of various backgrounds from as far away as Germany and New England. Already by this date its collection was global in scope, including writings ranging from a vocabulary of Algonquian to the Persian poetry of Saadi of Shiraz. That the college became embroiled in political controversy amidst the turmoil of the English Revolution testifies to its importance as an intellectual hub in the heart of London.