Indiana has three main landform regions: the Great Lakes Plain across the northern third, with moraines, kettle lakes and the sand dunes of Lake Michigan; the Tipton Till Plain, a flat to gently rolling glacial plain across the middle; and the Southern Hills and Lowlands, where knobs, limestone caves, sinkholes and wide river bottoms run down to the Ohio River. The highest point is Hoosier Hill in Wayne County at 383 m (1,257 ft), and the lowest, about 98 m (320 ft), is in Posey County where the Wabash River flows into the Ohio. That span of just 286 m (937 ft) is the narrowest of any US state without a coastline, spread over 94,326 km² (36,420 sq mi). Because the relief is so modest, the clearest way to read Indiana’s landforms is to start at the top and walk downhill. The state’s three highest named summits each sit at the head of a different landscape, and the Ohio River gathers them all at the bottom.
Hoosier Hill (383 m) and the Tipton Till Plain
Hoosier Hill is in Franklin Township in northern Wayne County, north-west of the hamlet of Bethel and about 18 km (11 mi) north of Richmond and Interstate 70. Its claimed height of 383 m comes from older satellite elevation data; newer USGS surveys put the top at about 382.7 m (1,255.5 ft). Either way, the summit is a patch of woods on private farmland, no more than about 9 m (30 ft) above the fields around it. When A. H. Marshall became the first person to stand on the high points of all 48 contiguous states in 1936, this was the last one he reached.
The hill is so gentle because it is buried. Geologically it belongs to the Dearborn Upland, a block of high ground in south-east Indiana that sits on the Cincinnati Arch, a broad upfold in the bedrock, and the upland averages about 335 m (1,100 ft) in elevation. But at Hoosier Hill the upland lies under a thick blanket of glacial debris, and on the surface that blanket is the Tipton Till Plain.
The till plain covers the central third of the state. It was laid down by ice sheets as a mixture of glacial clay, sand and gravel, and most of it lies between 180 and 300 m (600 and 1,000 ft) above sea level. Counties such as Howard are generally flat, while Morgan County is hillier, and the glacial sands, gravels and clays have weathered into exceptional farmland. Indianapolis, Muncie, Anderson and Kokomo all stand on it. The plain is broken only where rivers have cut down into it. The Wabash, 764 km (475 mi) long, crosses the state from north-east to south-west and then forms much of the Illinois border; it flows freely for 661 km (411 mi) from the dam near Huntington to the Ohio, which makes it the longest free-flowing river east of the Mississippi. In west-central Indiana, sandstone ravines line Sugar Creek at Turkey Run and Shades state parks, giving the flat country its most dramatic walls.
Sand Hill (328 m) Down to Mount Baldy: Moraines, Kettle Lakes and Dunes
Indiana’s second-highest named point, Sand Hill, stands at 328 m (1,076 ft) in Noble County in the north-east, and it belongs to a different glacial landscape. Northern Indiana is similar to the till plain, with elevations of 180 to 300 m, but it is ribbed with higher and hillier terminal moraines, ridges of debris dumped where the ice front stood still, and it is pocked with hundreds of kettle lakes. A kettle forms when a block of ice left behind by a retreating glacier is buried in sediment and later melts, leaving a hollow that fills with water. Kosciusko County holds the two best known: Tippecanoe Lake at Leesburg, 37 m (123 ft) deep and the deepest natural lake in Indiana, and Lake Wawasee near Syracuse, the largest natural lake wholly inside the state. The Indiana Department of Natural Resources lists about 900 lakes across the state.
Heading west and downhill, the moraines give way to low, wet ground. The Valparaiso Moraine, named after the Indiana town where it stands highest, swings around the southern end of Lake Michigan and carries the divide between the Great Lakes–St. Lawrence and Mississippi drainages. South of it, the Kankakee River once wandered through the Kankakee Marsh, one of the largest freshwater marshes in the country before it was drained for farming, and beyond that lies the eastern edge of the Grand Prairie that also covers much of Illinois. Nearer the lake, north-west Indiana has swell-and-swale topography: parallel sandy ridges that are the old beaches of an ancestral Lake Michigan, separated by marshy troughs. On dry ridges prickly pear cactus grows metres away from marsh plants in the swales.
The descent ends at the lake shore, about 176 m (577 ft) above sea level, and the lake frontage is itself a political choice. The original northern boundary of Ohio, Indiana and Illinois was meant to run through the southern tip of Lake Michigan, which would have left Indiana with no usable shore, so at statehood in 1816 the line was moved 16 km (10 mi) north. Along that shore the dunes rise to nearly 60 m (200 ft). Indiana Dunes National Park, authorised as a national lakeshore in 1966 and redesignated as the 61st national park on 15 February 2019, runs for about 24 km (15 mi) between Gary and Michigan City and covers 6,212 hectares (15,349 acres), with outlying units such as Pinhook Bog and the Hoosier Prairie.
Its best-known dune, Mount Baldy, is 38 m (126 ft) tall and is a “living dune” that moves each year. After climbers destroyed the marram grass that held it in place, it began advancing south toward its car park, and the piers at Michigan City make things worse by blocking the longshore drift that would otherwise feed it sand. The southern face is now closed to climbers.
Weed Patch Hill (322 m) and the Karst Below the Knobstone Escarpment
The third-highest named summit, Weed Patch Hill, reaches 322 m (1,058 ft) in Brown County State Park, and it crowns the most rugged terrain in Indiana. Weed Patch Hill is the high point of the Knobstone Escarpment, a bold ridge of steep hills, locally called knobs, that rises hundreds of feet above the Scottsburg Lowland to the east and runs about 240 km (150 mi) from southern Johnson County across the Ohio River into Kentucky. The escarpment is made of resistant siltstones from the upper Borden Group; the softer shales to the east wore down into the Scottsburg Lowland. The hills of Brown County, west of the escarpment, belong to the Norman Upland, where valley floors lie 120 to 150 m (400 to 500 ft) below the hilltops, and their autumn colours drew the painter T. C. Steele, who made his home in the county.
West of the Norman Upland the land drops again, onto the Mitchell Plain, a gently rolling surface underlain by thick, soluble limestones laid down in a shallow inland sea during the Mississippian period, about 360 to 325 million years ago. Rainwater has been dissolving that rock for millions of years, and the result is karst. The Lost River, about 140 km (87 mi) long, rises in Washington County and flows at least 37 km (23 mi) of its main course completely underground before emerging to join the East Fork of the White River in Martin County; in one square mile along its course there are as many as 1,022 sinkholes. Farther south, in Harrison and Crawford counties, the same process hollowed out Wyandotte Caves, which began forming about 2 million years ago, and Marengo Cave, first entered by two children on 6 September 1883 and open for tours ever since.
The limestone that makes the caves also made an industry. The Salem Limestone, sold as “Indiana limestone” or Bedford limestone, has been quarried in south-central Indiana for buildings across the country, including the Empire State Building, the Pentagon and Washington National Cathedral, and some 35 of the 50 state capitol buildings are made of it. Much of this hill country is now protected in the Hoosier National Forest, about 827 km² (204,303 acres), headquartered in Bedford.
The Ohio River: From the Falls of the Ohio to the Wabash Confluence (98 m)
Every stream in southern Indiana eventually reaches the Ohio, which forms the state’s entire southern boundary with Kentucky. The river has one great landform on the Indiana shore. At Clarksville, opposite Louisville, the Falls of the Ohio were a series of rapids where the river dropped 7.9 m (26 ft) over about 3 km (2 mi) across shelves of Jeffersonville Limestone, formed between about 387 and 380 million years ago in the Devonian. They were the only barrier to navigation on the whole river, and Louisville, Jeffersonville, Clarksville and New Albany all grew up where boats had to stop, unload or wait for local pilots. Lewis and Clark met here to begin their expedition.
Engineering tamed the falls in stages: the Louisville and Portland Canal and its locks bypassed them in 1830, and the McAlpine Locks and Dam later covered most of the rapids. What remains exposed at low water, best seen between August and October, is a bed of fossil corals preserved in their living positions, protected in Falls of the Ohio State Park.
Below Louisville the valley widens. About 12,000 km² (4,700 sq mi) of Indiana lies below 150 m (500 ft), mostly in the Ohio and lower Wabash valleys between Tell City, Evansville, Mount Vernon and Terre Haute. These flat, flood-prone bottomlands, where the Wabash, White and Ohio meet, shelter plants and animals more typical of the Lower Mississippi and the Gulf Coast. Settlement followed the rivers here first: Vincennes, founded by French traders on the Wabash in 1732, is the oldest town in the state, and Corydon, near the Ohio, was the first state capital. At the south-west corner, where Illinois, Indiana and Kentucky meet at the mouth of the Wabash, the land reaches its lowest point, about 98 m (320 ft) above sea level, though some surveys put the water surface there nearer 101 m.
From the buried upland at Hoosier Hill to the Posey County bottomlands, Indiana descends less than 300 m, yet it passes through moraines, dunes, knobs, caves and river falls on the way. For more on the southern hills, read our explainer on what karst topography is; to follow the river along the border, see our Ohio River geography guide; and for the state as a whole, turn to the complete guide to Indiana geography.