Puritan colonists in North America. The Cape's fifteen towns developed slowly, aside from Barnstable (1639), Sandwich (1637), and Yarmouth (1639). The final town to be established on the Cape was Bourne in 1884, breaking off from Sandwich. Provincetown was a group of huts until the 18th century. A channel from Massachusetts Bay to Buzzards Bay is shown on Southack's map of 1717. The present Cape Cod Canal was slowly developed from 1870 to 1914. The federal government purchased it in 1928. The Cape's vegetation was depauperate and trees were scarce by the time that Henry Thoreau saw Cape Cod during his four visits over 1849 to 1857, because of early colonial settlement and intensive land use. The settlers heated by fires, and it took 10 to 20 cords (40 to 80 m3) of wood to heat a home, so they cleared most of Cape Cod of timber early on. They planted familiar crops, but these were unsuited to Cape Cod's thin, glacially derived soils. For instance, much of Eastham was planted to wheat. The settlers practiced burning of woodlands to release nutrients into the soil. Improper and intensive farming led to erosion and the loss of topsoil. Farmers grazed their cattle on the grassy dunes of coastal Massachusetts, only to watch "in horror as the denuded sands 'walked' over richer lands, burying cultivated fields and fences." Dunes on the outer Cape became more common, and many harbors filled in with eroded soils. By 1800, much of Cape Cod's firewood had to be transported by boat from Maine. The paucity of vegetation was worsened by the raising of merino sheep that reached its peak in New England around 1840. The early industrial revolution occurred through much of Massachusetts and Rhode Island, but it mostly bypassed Cape Cod due to a lack of significant water power in the area. The Cape developed as a large fishing and whaling center as a result, and also because of its geographic position. After 1860 and the opening of the American West, farmers abandoned agriculture on the Cape. By 1950, forests had recovered to an extent not seen since the 18th century. Modern era Cape Cod became a summer haven for city dwellers beginning at the end of the 19th century. Improved rail transportation made the towns of the Upper Cape, such as Bourne and Falmouth, accessible to Bostonians. At the beginning of the twentieth century,