The Federal Dam is a manmade dam built across the Hudson River in the U.S. state of New York from Troy on the east bank to Green Island on the west bank. The major function of the dam is to improve navigability. It is located at mile 153 of the Hudson River, measuring from the beginning of the Hudson as a Federally Navigable Waterway near the Battery in Manhattan. The location of the dam marks the upper end of the Hudson River estuary.