The range of western yellow pine covers a million square miles. Its eastern boundary is a line drawn from South Dakota to western Texas. The species covers much of the country between that line and the Pacific ocean. It is natural that it should have more names than one in a region so extensive. It is best known as western yellow pine, but lumbermen often call it California white pine. The standing timber is frequently designated bull pine, but that name is not often given to the lumber. Where there is no likelihood of confusing it with southern pines, it is called simply yellow pine. The name heavy-wooded pine, sometimes applied to the lumber in England, is misleading. When well seasoned it weighs about thirty pounds per cubic foot, and ordinarily it would not be classed heavy. In California it is called heavy pine, but that is to distinguish it from sugar pine which is considerably lighter. The color of its bark has given it the name Sierra brownbark pine. The same tree in Montana is called black pine. The tree has developed two forms. Some botanists have held there are two species, but that is not the general opinion. In the warm, damp climate of the Pacific slope the tree is larger, and somewhat different in appearance from the form in the Rocky Mountain region. The same observation holds true of Douglas fir. The wood of western yellow pine is medium light, not strong, is low in elasticity, medullary rays prominent but not numerous; resinous, color light to reddish, the thick sapwood almost white. The annual rings are variable in width, and the proportionate amounts of springwood and summerwood also vary. It is not durable in contact with the ground. The wood is easy to work and some of the best of it resembles white pine, but as a whole it is inferior to that wood, though it is extensively employed as a substitute for it in the manufacture of doors, sash, and frames. It is darker than white pine, harder, heavier, stronger, almost exactly equal in stiffness, but the annual rings of the two woods do not bear close resemblance. The tree reaches a height of from 100 to 200 feet, a diameter from three to seven. It is occasionally much larger. Its size depends much on its habitat. The best development occurs on the Sierra Nevada mountains in California and the best wood comes from that region, though certain other localities produce high-grade lumber.