The sheer abundance of lumber in North America made lumber mills one of the earliest industrialized buildings to be created in the colonies. Prior to the construction of the first lumber mills, it was often necessary to balance extremely long pieces of timber on the edges of pits or gulleys in order to properly prepare the wood, which proved to be a slow and dangerous process. Beginning in the 1640s, across the eastern coast of North America, rivers, creeks, and streams were dammed in order to power the many mills cropping up across the continent. In the American South, many plantations, because of their high demand for fresh timber, had their own lumber mills which could run nearly unmanned. This allowed the plantation's labor to focus on the collection of cotton or tobacco rather than sawing wood.