Tappan Zee. The Tappan Zee is a natural widening of the Hudson River, about 3 mi across at its widest, in southeastern New York in the United States. It stretches about 10 mi along the boundary between Rockland and Westchester counties, downstream from Croton Point to Irvington. It derives its name from the Tappan Native American sub-tribe of the Delaware/Lenni Lenape, and the Dutch word zee, meaning a sea. Flanked to the west by high steep bluffs of the Palisades, it forms something of a natural lake on the Hudson about 10 mi north of Manhattan. Communities along the Tappan Zee include Nyack on the western side as well as Ossining and Tarrytown on the eastern side. It was formerly crossed by the original Tappan Zee Bridge, opened in 1955 and about 3.1 mi long, connecting Nyack and Tarrytown. Today, it is crossed by the new Tappan Zee Bridge, which opened in 2017 and 2018 at about the same length as the old bridge. On September 14, 1609, the explorer Henry Hudson entered the Tappan Zee while sailing upstream from New York Harbor. At first, Hudson believed the widening of the river indicated that he had found the Northwest Passage. He proceeded upstream as far as present-day Troy before concluding that no such strait existed there. The Tappan Zee is mentioned several times in Washington Irving's famous short story, The Legend of Sleepy Hollow. The tale is set in the vicinity of Tarrytown, in the area near Irving's own home at Sunnyside.