The next transport of sheep to North America was not until 1607, with the voyage of the Susan Constant to Virginia. However, the sheep that arrived in that year were all slaughtered because of a famine, and a permanent flock was not to reach the colony until two years later in 1609. In two decades' time, the colonists had expanded their flock to a total of 400 head. By the 1640s there were about 100,000 head of sheep in the 13 colonies, and in 1662, a woolen mill was built in Watertown, Massachusetts. Especially during the periods of political unrest and civil war in Britain spanning the 1640s and 1650s which disrupted maritime trade, the colonists found it pressing to produce wool for clothing. Many islands off the coast were cleared of predators and set aside for sheep: Nantucket, Long Island, Martha's Vineyard and small islands in Boston Harbor were notable examples. There remain some rare breeds of American sheep—such as the Hog Island sheep—that were the result of island flocks. Placing semi-feral sheep and goats on islands was common practice in colonization during this period. Early on, the British government banned further export of sheep to the Americas, or wool from it, in an attempt to stifle any threat to the wool trade in the British Isles. One of many restrictive trade measures that precipitated the American Revolution, the sheep industry in the Northeast grew despite the bans.
