East River, a strait connecting New York bay with Long Island sound, about 18 m. long, and between New York and Brooklyn about three fourths of a mile wide. It leaves the sound at a point called Throg's neck, where there is a lighthouse with a fixed light, and where Fort Schuyler defends the N. E. approach to New York; and it enters the bay S. E. of Manhattan island, between the metropolis and Brooklyn. It also communicates with the Hudson by a narrow channel called Harlem river and Spuyten Duyvel creek, which separate Manhattan island from the mainland. It has a rapid current caused by the tide from the Atlantic, which, gathering force as it flows W. into the narrowest part of the sound, reaches its greatest height in the East river, arrives at New York three quarters of an hour earlier than that which rises in the bay, and drives upward along the E. shore of the Hudson many miles in advance of the tide on the W. shore. The East river is navigable by vessels of the largest size, and is crossed by numerous steam ferries.

It contains several islands, and has a pass called Hellgate, 7 m. from New York bay, the navigation of which is attended with considerable danger; but extensive blasting operations are now (1874) in progress at the expense of the United States government to remove all the obstacles to navigation. (See Blasting.)