Hudson River. The Hudson River is a 315-mile river that flows from north to south primarily through eastern New York in the United States. The river originates in the Adirondack Mountains of Upstate New York, flows southward through the Hudson Valley to the Upper New York Bay between New York City and Jersey City. It eventually drains into the Atlantic Ocean at New York Harbor. The river serves as a political boundary between the states of New Jersey and New York at its southern end. Further north, it marks local boundaries between several New York counties. The lower half of the river is a tidal estuary, deeper than the body of water into which it flows, occupying the Hudson Fjord, an inlet which formed during the most recent period of North American glaciation, estimated at 26,000 to 13,300 years ago. Tidal waters influence the Hudson's flow from as far north as the city of Troy. The river is named after Henry Hudson, an Englishman sailing for the Dutch East India Company, who explored it in 1609, and after whom Hudson Bay in Canada is also named. It had previously been observed by Italian explorer Giovanni da Verrazzano sailing for King Francis I of France in 1524, as he became the first European known to have entered the Upper New York Bay, but he considered the river to be an estuary. The Dutch called the river the North River-with the Delaware River called the South River-and it formed the spine of the Dutch colony of New Netherland. Settlements of the colony clustered around the Hudson, and its strategic importance as the gateway to the American interior led to years of competition between the English and the Dutch over control of the river and colony. During the eighteenth century, the river valley and its inhabitants were the subject and inspiration of Washington Irving, the first internationally acclaimed American author. In the nineteenth century, the area inspired the Hudson River School of landscape painting, an American pastoral style, as well as the concepts of environmentalism and wilderness. The Hudson was also the eastern outlet for the Erie Canal, which, when completed in 1825, became an important transportation artery for the early-19th-century United States. Counties Hamilton Essex Warren Washington Saratoga Albany Rensselaer Greene Columbia Ulster Dutchess Putnam Orange Rockland Westchester Bronx Bergen, NJ Hudson, NJ New York. The source of the Hudson River is Lake Tear of the Clouds in the Adirondack Park at an altitude of 4,322 feet. However, the river is not cartographically called the Hudson River until miles downstream. The river is named Feldspar Brook until its confluence with the Opalescent River, and then is named the Opalescent River until the river reaches Calamity Brook, flowing south from the outlet of Henderson Lake. From that point on, the stream is cartographically known as the Hudson River. The U.S. Geological Survey uses this cartographical definition. The longest source of the Hudson River as shown on the most detailed USGS maps is the Opalescent River on the west slopes of Little Marcy Mountain, originating two miles north of Lake Tear of the Clouds, several miles, past the Flowed Lands, to the Hudson River. and a mile longer than Feldspar Brook, which flows out of that lake in the Adirondack Mountains. Popular culture and convention, however, more often cite the photogenic Lake Tear of the Clouds as the source. Using river names as seen on maps, Indian Pass Brook flows into Henderson Lake, and the outlet from Henderson Lake flows east and meets the southwest flowing Calamity Brook. The confluence of the two rivers is where maps begin to use the Hudson River name. South of the outlet of Sanford Lake, the Opalescent River flows into the Hudson. The Hudson then flows south, taking in Beaver Brook and the outlet of Lake Harris. After its confluence with the Indian River, the Hudson forms the boundary between Essex and Hamilton counties. In the hamlet of North River, the Hudson flows entirely in Warren County and takes in the Schroon River. Further south, the river forms the boundary between Warren and Saratoga Counties. The river then takes in the Sacandaga River from the Great Sacandaga Lake. Shortly thereafter, the river leaves the Adirondack Park, flows under Interstate 87, and through Glens Falls, just south of Lake George although receiving no streamflow from the lake. It next goes through Hudson Falls.