maple, common name for the genus Acer of the Aceraceae, a family of deciduous trees and shrubs of the Northern Hemisphere, found mainly in temperate regions and on tropical mountain slopes. Acer, the principal genus, includes the many maples and the box elder. Maples are popular as shade trees and often have brilliantly colored foliage in the fall. Several E North American species provide valuable timber, notably the sugar, hard, or rock, maple (A. saccharum), and the more brittle-timbered black maple (A. nigrum). Their strong, close-grained, easily worked hardwood is used in shipbuilding and aircraft construction, for floors, fuel, and wood pulp, and in many other industries. Bird's-eye and curly maple are decorative cuts used for cabinetmaking. In addition, these two maples are the main sources of maple sugar. A prevalent and widely distributed North American species is the swamp, or red, maple (A. rubrum). The box elder, or ash-leaved maple (A. negundo), is a smaller North American species also planted as a shade tree; its softer wood is used for woodenware, cheap furniture, and paper pulp. Several European and Japanese maples have been introduced to the United States as ornamentals. The only other genus of the family is Dipteronia, consisting of two species indigenous to China. All members of the family have characteristic winged fruits. Maple syrup is the concentrated sap obtained for commercial purposes from the sugar maple and the black maple. Sap flows intermittently for periods of up to six weeks in the spring, is caught in buckets, strained, and concentrated by boiling to a density of 11 lb (4.9 kg) per gal for syrup or evaporated further for sugar. The syrup and sugar, first prepared by Native Americans (by dropping hot rocks into the sap or by freezing out the water) became the staple sweetening used by the colonists and remained important until c.1875. As cane sugar-with a higher saccharine content and a lower manufacturing cost-gained precedence and as the maple forest stands, or "sugar bush," were depleted, maple sugar and syrup became scarcer and are now used mainly for confectionery and for flavoring, especially of tobacco. Vermont and New York are the chief producing states. Maples are classified in the division Magnoliophyta, class Magnoliopsida, order Sapindales, family Aceraceae.