By the early 1800s, family farms covered southern New England, and most of the land had been cleared of trees. For generations, farmers cut down trees, drained swamps, hauled rocks out of their fields, and built fences to control livestock. New England farmers built several kinds of fences, including zigzag fences, also known as worm fences or Virginia rail fences, which were easy to build but used lots of wood, as well as post and rail fences, tighter board fences around gardens to keep out pests, and stone walls, the most permanent kind of farm fence. Clearing the forest was back-breaking work done with axes, farm carts, and teams of oxen. In some towns, more than eighty percent of the land was open by 1830. Since 1860 or so, the number of farms has been declining in New England, and most of those farm fields are now forest again.