The Delaware River is a river on the Atlantic coast of the United States for the first time mapped the Dutch expedition led by Henry Hudson in 1609. The River was christened South River in the colony of New Netherland, which, unlike the North River, the Hudson River was then known as. The name Delaware, Sir Thomas West 3-5th Baron de La Warr, English was used and became standard after the English conquest of New Holland in the year 1664.