During the 20th century, gull populations in North America experienced considerable changes in abundance and geographic ranges. The objective of this study was to describe population trends of Herring Gulls (Larus argentatus) and Great Black-backed Gulls (L. marinus) in the New York Bight, USA, over a 40-year period (1974–2013). A variety of data sources using different survey methods provided estimates of the number of breeding pairs for both species. In the Long Island portion of the New York Bight, overall Herring and Great Black-backed gull nesting populations appear to have fluctuated considerably in size during this time period, and the largest numbers of breeding individuals of these two species occurred in the 1980s. In coastal New Jersey, the Herring Gull nesting population has remained relatively constant, whereas the Great Black-backed Gull nesting population has increased. Individual nesting colonies are dynamic and can vary in size considerably during even short time periods. Several factors, including sea-level changes and the availability of anthropogenic food sources (i.e., at landfills and fisheries by-catch), likely have strongly influenced individual colonies and the overall Herring and Great Blackbacked gull breeding populations in the New York Bight.