The North Atlantic right whale was once abundant in coastal waters on both sides of the North Atlantic Ocean but is now one of the world's most endangered species of mammal, terrestrial or marine. Only a single population numbering about 300 whales survives in the North Atlantic. At least two separate populations existed historically. Commercial hunting that began in the 11th century and continued through the early 1900s eliminated the eastern population along the coast of Europe. Basque whalers in the Gulf of St. Lawrence in the mid-1500s first exploited the western population, whose remnants are now found primarily along the coast of North America between Florida and southeastern Canada. By the early 1600s thousands of western North Atlantic right whales had been killed, and by the early 1900s, its survivors numbered only a few hundred whales at most, and perhaps just a few tens of animals. With the exception of the eastern North Pacific right whale population found off Alaska in summer, the western North Atlantic right whale population is the most endangered marine mammal population in U.S. waters.