KYKentucky Geography

There is a piece of Kentucky you cannot drive to from Kentucky. The Mississippi swings through a hairpin near New Madrid, and inside that loop sits roughly seventeen square miles of Fulton County, surrounded by Missouri on the water side and Tennessee on the land side. Fewer than twenty people live in the Kentucky Bend, and the only road in comes through Tiptonville, Tennessee. Children there are schooled in Tennessee, mail arrives with a Tennessee route, and the county courthouse is a hundred road miles away.

Why Kentucky owns the entire Ohio River

Most river boundaries run down the middle of the channel. Kentucky's does not. When Virginia ceded its western county in 1792, the northern limit was fixed at the low-water mark on the far bank of the Ohio, so the whole riverbed belongs to Kentucky and Ohio, Indiana and Illinois begin where the water once stopped. The Supreme Court has been asked about it repeatedly, and in 1980 it confirmed that the line is where the low-water mark stood in 1792, not where it stands now.

Two centuries of channel migration have made that awkward. Green River Island, opposite Evansville, ended up physically attached to Indiana when the river abandoned the chute behind it, and in 1890 the Court held it was still Kentucky. The southern boundary has its own survey scars: the line with Tennessee was meant to follow 36 degrees 30 minutes north, but Thomas Walker's 1780 survey wandered several miles off, and the jogs where later surveyors refused to agree with him are still on the map. Seven states touch Kentucky in all, more than touch all but a handful: Missouri, Illinois, Indiana, Ohio, West Virginia, Virginia and Tennessee.

Black Mountain down to the Mississippi

Kentucky's ceiling is Black Mountain in Harlan County at 4,145 feet, on the Virginia line and long owned by coal companies. Its floor is the Mississippi River in Fulton County at 257 feet, which happens to be inside the same isolated bend. That is a 3,888-foot range in a state ranked 37th in area.

Between them, the state runs through five sharply different provinces. The Eastern Coal Field, part of the Cumberland Plateau, is dissected sandstone country with narrow hollows. The Bluegrass sits on the Cincinnati Arch, an upwarp that has stripped away younger rock and exposed Ordovician limestone unusually rich in phosphorus and calcium, which is the actual reason horses have been bred on that specific ground for two hundred years. A crescent of steep conical hills called the Knobs rings the Bluegrass, shale cones capped with resistant sandstone. West of that lies the Pennyroyal, then the Western Coal Field around the lower Green River, then the Jackson Purchase.

The Purchase is the newest part of the state, eight counties between the Tennessee and Mississippi rivers bought from the Chickasaw in 1818 in a treaty negotiated by Andrew Jackson and Isaac Shelby. It sits on the New Madrid Seismic Zone, the source of the enormous 1811 and 1812 earthquakes, and remains the most seismically active ground in Kentucky.

Limestone, sinkholes and the longest cave on earth

Under the Pennyroyal, water has been dissolving Mississippian limestone for millions of years, producing sinkhole plains where surface streams disappear into the ground and reappear miles away. The result is Mammoth Cave, where surveyors have now mapped more than 400 miles of connected passage. The next longest known cave system in the world, in Mexico, is roughly half that. Mammoth stays open and dry because a hard layer, the Big Clifty Sandstone, caps the limestone like a roof and keeps the upper levels from collapsing. The park was established in 1941 and added to the World Heritage list in 1981.

The same rock produces the state's stranger water features. Cumberland Falls, 68 feet high and 125 feet across, throws enough mist on clear nights around the full moon to produce a moonbow, one of very few places in the western hemisphere where a lunar rainbow appears on a predictable schedule. In the sandstone country of the Daniel Boone National Forest, the Red River Gorge holds more than a hundred natural arches, the densest concentration east of the Rockies. At Big Bone Lick in Boone County, salt springs trapped mammoths and mastodons whose bones, shipped east in the 1700s, effectively started American vertebrate paleontology.

The clock line and the lake line

Kentucky is cut by two artificial north-south divisions. The first is the time zone boundary: Louisville, Lexington and Frankfort keep Eastern Time, while Owensboro, Bowling Green, Paducah and Mammoth Cave itself keep Central. The second is water. The state counts roughly 1,900 miles of commercially navigable river, more than any state except Alaska, and much of it was rebuilt in the twentieth century. When TVA closed Kentucky Dam on the Tennessee River in 1944, the reservoir behind it was the largest artificial lake in the country by surface area. Barkley Dam did the same to the Cumberland in 1966, and a canal now joins the two. The strip of land trapped between them became Land Between the Lakes, about 170,000 acres of peninsula that was farm country within living memory.

Weather extremes on record

The hottest reading is 114 degrees at Greensburg on July 28, 1930. The coldest is 37 below zero at Shelbyville on January 19, 1994. Rainfall runs around 45 to 50 inches a year, heavier in the west, and the combination of steep hollows and saturated ground in the eastern coalfield makes flash flooding the state's most persistent hazard rather than the tornadoes people expect.

Bordering states and more Kentucky pages