INIndiana Geography

Ask what makes Indiana geographically peculiar and the honest first answer is the clock. Twelve of the state's 92 counties keep Central Time and the other 80 keep Eastern. Six of the Central counties cluster in the northwest corner where commuters look toward Chicago: Lake, Porter, LaPorte, Newton, Jasper and Starke. The other six sit in the southwest around Evansville: Gibson, Posey, Vanderburgh, Warrick, Spencer and Perry.

For decades the arrangement was messier still. Most of Indiana refused daylight saving time and stayed on standard time year round, so the state's relationship to its neighbours flipped twice a year. A 2005 law ended the holdout, and from April 2006 the entire state has observed daylight saving, though the two zone split remains.

Kentucky owns the whole Ohio River

Indiana's southern boundary is not the middle of the Ohio River. Virginia's 1792 cession, which created Kentucky, set the line at the low water mark on the river's northwestern bank as it stood that year. Every drop of the Ohio therefore belongs to Kentucky, and Indiana's territory technically ends at the water's edge.

Locks and dams have since raised the pool by several feet, so the 1792 low water line now lies submerged along much of the frontier. The Supreme Court reaffirmed the historic mark in litigation during the 1980s, which means Indiana's legal border in places runs underwater a short distance out from the visible shore. The lowest ground in the state, 320 feet, is where the Wabash empties into the Ohio in Posey County. The highest, Hoosier Hill in Wayne County at 1,257 feet, is a low rise at the edge of a soybean field. Total relief comes to 937 feet across 36,420 square miles, the smallest area of any state in the continental interior west of the Appalachians.

Limestone under the southern third

South central Indiana sits on the Salem Limestone, a bed of fine grained Mississippian rock deposited in a shallow sea roughly 340 million years ago. Quarries around Bedford and Bloomington have shipped it out since the 1820s. The Empire State Building wears it, the Pentagon wears it, and so do a long list of state capitols and cathedrals.

Where that limestone reaches the surface it dissolves. The Mitchell Plain is pitted with sinkholes, and beneath it run some of the most extensive cave systems in the country. Bluespring Caverns near Bedford contains about three miles of navigable underground river, the longest in the United States, toured by boat. Marengo Cave and Wyandotte Cave sit nearby. The Lost River in Orange County drops into swallow holes and travels roughly 22 miles underground before resurfacing at the Rise near Orangeville.

Where the ice stopped

Draw a line across Indiana at about the latitude of Bloomington and you have the approximate southern limit of the Wisconsin glaciation. North of it the land is flat to gently rolling, blanketed in till and dotted with moraines and kettle lakes. South of it the hills survive, because the last ice never got there to plane them down.

Geologists split the state into three broad belts: the Northern Moraine and Lake Region, the Central Till Plain that carries most of the corn ground, and the Southern Hills and Lowlands where the uplands and karst sit. Brown County's ridges and the sandstone gorges of Turkey Run and Shades exist because the ice quit before reaching them.

Northern Indiana's lakes are glacial leftovers. Lake Wawasee is the largest natural one at about 3,400 acres, while Monroe Lake, a 1960s reservoir on Salt Creek, is the largest body of water in the state at roughly 10,750 acres.

Forty five miles of Lake Michigan

When Indiana applied for statehood in 1816, Congress pushed the northern boundary ten miles above the southern tip of Lake Michigan. That adjustment handed the new state roughly 45 miles of lakefront and, eventually, a deepwater port at Burns Harbor.

The same shoreline holds Indiana Dunes National Park, redesignated from a national lakeshore in February 2019 and the only national park in the state. Its dunes sit wedged between the steel mills of Gary and Portage, and Mount Baldy, a bare sand dune near Michigan City, migrates inland by a few feet each year, burying trees as it goes.

The Wabash and the portage at Fort Wayne

The Wabash runs 503 miles from western Ohio to the Ohio River and, below the reservoir at Huntington, carries no dams on its main stem, which makes it the longest free flowing river east of the Mississippi. It forms about 200 miles of the Illinois border on its way south.

At Fort Wayne the St. Joseph and St. Marys rivers join to create the Maumee, which flows northeast to Lake Erie. The Wabash headwaters begin a few miles away and flow to the Gulf of Mexico. The strip of ground between them was the portage that made Fort Wayne strategically valuable, and it later carried the Wabash and Erie Canal, at about 468 miles the longest canal ever dug in North America.

Indiana's temperature records show the reach of both air masses that cross it: 116 degrees at Collegeville in July 1936 and 36 below zero at New Whiteland in January 1994.

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