The Three Rivers Surrounding Manhattan Island

Manhattan Island is bounded by three distinct waterways — two rivers and one tidal strait:

The Three Waterways

Waterway	Side	Type	Key Details
Hudson River	West	River (estuarine lower section)	315 mi from Adirondacks; tidal to Troy, NY; separates Manhattan from NJ
East River	East	Tidal strait (not a river)	16 mi; connects Long Island Sound to NY Harbor; separates Manhattan from Brooklyn/Queens
Harlem River	North/Northeast	Tidal strait (engineered)	8 mi; connects Hudson to East River; separates Manhattan from Bronx

East River & Harlem River are tidal straits — saltwater channels connecting larger bodies, with reversing currents, not freshwater rivers with single sources
Hudson River is a true river (freshwater source: Lake Tear of the Clouds) but its lower 153 miles are a drowned river valley (ria) with tidal influence
Manhattan is an island — completely surrounded by water
Spuyten Duyvil Creek (filled/altered) historically connected Harlem River to Hudson at north tip; now largely replaced by Harlem River Ship Canal (1895)

Waterway	Major Crossings
Hudson River	George Washington Bridge, Lincoln Tunnel, Holland Tunnel, Tappan Zee Bridge (upstream)
East River	Brooklyn Bridge, Manhattan Bridge, Williamsburg Bridge, Queensboro Bridge, RFK Bridge, 4 subway tunnels
Harlem River	Broadway Bridge, University Heights Bridge, Washington Bridge, Alexander Hamilton Bridge, High Bridge (pedestrian), Macombs Dam Bridge, 3 subway bridges

Estuarine System: Hudson-Raritan Estuary — nursery for fish, shellfish, birds
Commerce: Port of NY/NJ (3rd largest US) on Upper Bay, Kill Van Kull, Arthur Kill
Recreation: Hudson River Park, East River Esplanade, Harlem River Greenway
History: Lenape "Mannahatta" ("hilly island"); Dutch New Amsterdam (1624); British NY (1664)