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, the farthest reach of tidal influence.

The Federal Lock

In order to allow ships to move freely, the eastern end of the dam contains a lock, commonly called the Federal Lock or (on some charts and publications) the "Troy-US Lock." The lock, which was opened in 1916, has a single chamber and is 520 ft long, 45 ft wide, 17 ft deep, and has a lift of approximately 14 feet (4.3 m). Although it is the first lock encountered by vessels passing from the Hudson River into the Great Lakes by way of the New York State Canal System, and it is sometimes referred to as lock "E-1," it is not part of the Erie Canal (which officially has no "Lock 1"), nor maintained by the New York State Canal Corporation. Both the lock and the dam were built and are currently operated by the U.S. Army Corps of Engineers; as of September 2006, it was listed as being in "Operational" condition.