Coney Island was originally a true barrier island separated from the mainland of Brooklyn by Coney Island Creek, a narrow and shallow waterway. However, as the area developed into a major tourism and residential hub in the early 20th century, the creek became an obstacle to progress. In the 1920s and 1930s, the city began filling in portions of the creek to allow for the construction of roads and the expansion of the subway system. The most significant change occurred during the tenure of Robert Moses in the 1940s, when the Belt Parkway was constructed. To facilitate this massive infrastructure project, a large section of the creek was filled in with earth and sand, effectively physically anchoring the "island" to the rest of Long Island. While it retains the name "Coney Island" for historical and cultural reasons, it is geographically a peninsula. Today, only a small, stagnant portion of the original creek remains on the western side, serving as a reminder of the waterway that once allowed boats to circumnavigate the legendary amusement district.