East River

The East River is a saltwater tidal estuary or strait in New York City. The waterway, which is not a river despite its name, connects Upper New York Bay on its south end to Long Island Sound on its north end. It separates Long Island, with the boroughs of Brooklyn and Queens, from Manhattan Island, and from the Bronx on the North American mainland. The East River forms the eastern boundary of Manhattan Island, whereas the island's western boundary is formed by the Hudson River.

Because of its connection to Long Island Sound, it was once also known as the Sound River. The tidal strait changes its direction of flow regularly, and is subject to strong fluctuations in its current, which are accentuated by its narrowness and variety of depths. The waterway is navigable for its entire length of 16 miles (26 km), and was historically the center of maritime activities in the city.





== Formation and description ==



Technically a drowned valley, like the other waterways around New York City, the strait was formed approximately 11,000 years ago at the end of the Wisconsin glaciation. The distinct change in the shape of the strait between the lower and upper portions is evidence of this glacial activity. The upper portion (from Long Island Sound to Hell Gate), running largely perpendicular to the glacial motion, is wide, meandering, and has deep narrow bays on both banks, scoured out by the glacier's movement.