In his monographic article on Michelangelo's Laurentian Library in Florence, first published in 1934, Rudolf Wittkower relegated the history of its siting within the canonica (claustral buildings) of San Lorenzo to a third appendix. Since then a number of scholars have given detailed consideration to the site history, realizing it to be a significant aspect of Michelangelo's early career as an architect. The present paper maintains that some study of the canonica as Michelangelo probably encountered it should be prerequisite to any account of the site and presents new observations, measurements, and previously unnoticed 18th-century plans preserved in Prague to make such a study. The comprehensive publication of Michelangelo's correspondence, records, and drawings during the past 20 years facilitates reconstruction of the sequence of events in his development of the site, and this further illuminates the artist's working methods and relations with both his patron and his assistant. Consideration is also given to an abandoned idea for a library beyond the confines of the canonica, bordering on piazza San Lorenzo and perpendicular to the church façade. Documents from the Florence State Archive confirm the identity and location of properties as shown on Michelangelo's own plan of the vicinity, which is newly oriented, and the rejected scheme is briefly examined in relation to contemporary urban redevelopment in Florence.