Kentucky is known as the "Bluegrass State", a nickname based on the fact that native bluegrass is present in many of the pastures throughout the state, based on the fertile soil. It made possible the breeding of high-quality livestock, especially thoroughbred racing horses. It is a land with diverse environments and abundant resources, including the world's longest cave system, Mammoth Cave National Park; the greatest length of navigable waterways and streams in the Lower 48 states; and the two largest man-made lakes east of the Mississippi River. It is also home to the highest per capita number of deer and turkey in the United States, the largest free-ranging elk herd east of Montana, and the nation's most productive coalfield. Kentucky is also known for thoroughbred horses, horse racing, bourbon distilleries, bluegrass music, automobile manufacturing, tobacco and college basketball.