early 19th century United States. Pollution in the river increased in the 20th century, more acutely by mid-century, particularly with industrial contamination from polychlorinated biphenyls (PCBs). Pollution control regulations, enforcement actions and restoration projects initiated in the latter 20th century have begun to improve water quality, and restoration work has continued in the 21st century. Names The river was called or Ca-ho-ha-ta-te-a ("the river") by the Haudenosaunee, and it was known as ("river that flows two ways" or "waters that are never still") or by the Mohican nation who formerly inhabited both banks of the lower portion of the river. The meaning of the Mohican name comes from the river's long tidal range. The Delaware Tribe of Indians (Bartlesville, Oklahoma) considers the closely related Mohicans to be a part of the Lenape people, and so the Lenape also claim the Hudson as part of their ancestral territory, also calling it . The first known European name for the river was the Rio San Antonio as named by the Portuguese explorer in Spain's employ, Estêvão Gomes, who explored the Mid-Atlantic coast in 1525. Another early name for the Hudson used by the Dutch was Rio de Montaigne. Later, they generally termed it the Noortrivier, or "North River", the Delaware River being known as the Zuidrivier, or "South River". Other occasional names for the Hudson included Manhattes rieviere "Manhattan River", Groote Rivier "Great River", and de grootte Mouritse reviere, or "the Great Mouritse River" (Mourits is a Dutch surname). The translated name North River was used in the New York metropolitan area up until the early 1900s, with limited use continuing into the present day. The term persists in radio communication among commercial shipping traffic, especially below the Tappan Zee. The term also continues to be used in names of facilities in the river's southern portion, such as the North River piers, North River Tunnels, and the North River Wastewater Treatment Plant. It is believed that the first use of the name Hudson River in a map was in a map created by the cartographer John Carwitham in 1740. In 1939, the magazine Life described the river as "America's Rhine", comparing it to the stretch of the Rhine in Central and Western Europe. The tidal Hudson is unusually straight for a river, and the earliest colonial Dutch charts of the Hudson River designated the narrow, meandering stretches as racks, or reaches. These