a state located on the border between the Midwest and South of the United States. Kentucky is one of four U.S. states constituted as a commonwealth (the others being Virginia, Pennsylvania, and Massachusetts). Originally a part of Virginia, in 1792 Kentucky became the 15th state to join the Union. Kentucky is the 37th most extensive and the 26th most populous of the 50 United States.

Kentucky is known as the "Bluegrass State", a nickname based on the bluegrass found in many of its pastures because of the fertile soil. 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 contiguous United States; and the two largest man-made lakes east of the Mississippi River.

Kentucky 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 horse racing, bourbon distilleries, automobile manufacturing, tobacco, and college basketball.

Kentucky can be divided into five primary regions: the Cumberland Plateau in the east, the north-central Bluegrass region, the south-central and western Pennyroyal Plateau, the Western Coal Fields and the far-west Jackson Purchase.

The Bluegrass region is commonly divided into two regions, the Inner Bluegrass—the encircling 90 miles (145 km) around Lexington—and the Outer Bluegrass—the region that contains most of the Northern portion of the state, above the Knobs. Much of the outer Bluegrass is in the Eden Shale Hills area, made up of short, steep, and very narrow hills.
This map is a rough depiction of the regions because it relies largely on county lines; as a result, the Inner Bluegrass appears larger than it is, and the Cumberland Plateau appears slightly smaller. The latter region is more commonly known in Kentucky as the East Kentucky Coal Field. Note the singular; these regions are not the sites of coal "fields" but one continuous field with many overlapping seams; the West Kentucky Coal Field is part of the Illinois Basin.