The use of 200 public libraries in New York City was analyzed according to their neighborhood characteristics. In addition to demographic, economic, and cultural factors traditionally considered, the social and spatial interactions within a neighborhood were related to public library use. Correlation and regression analyses were implemented for all the libraries. The research found that traditional factors are not enough to explain public library use, especially in a cosmopolitan area such as New York City. Social connections and racial diversity and integration stimulate public library use. Based on these findings, suggestions were made for improving the underutilized library branches in disadvantaged neighborhoods.