What Did the Midwest Look Like Before Farming?

Before European-American settlers broke the sod, the Midwest was a vast, shifting mosaic of tallgrass prairie, oak savanna, wetlands, and dense hardwood forest, all sitting atop landforms sculpted by glaciers that had retreated only a few thousand years earlier. The landscape was not a static wilderness. It was actively shaped by climate, fire, enormous herds of bison, and the deliberate land-management practices of Indigenous peoples who had lived there for millennia. What settlers in the 1800s encountered was not “untouched nature” but rather the product of deep geological history layered with thousands of years of human influence.

A Landscape Built by Ice

The physical foundation of the Midwest was laid by the Laurentide Ice Sheet, which at its southern maximum around 20,000 years ago extended across what is now Wisconsin, Minnesota, Iowa, Illinois, Indiana, Michigan, and Ohio. As the ice advanced and retreated, it flattened older river valleys, deposited enormous volumes of sediment, and completely rearranged drainage networks across the region.¹ The flat-to-gently-rolling terrain that later made the region so attractive for plowing was itself a glacial product: till plains left behind as the ice melted, punctuated by moraines, drumlins, and outwash fans where meltwater dumped gravel and sand.

In north-central Wisconsin, the terminal positions of ice lobes left behind broad zones of hummocky topography containing ice-walled lake plains, ridges, and outwash deposits. Buried ice lingered under thick layers of debris, kept frozen by late-glacial permafrost, and did not melt away until after roughly 13,000 years ago when the climate warmed enough to thaw the permafrost.² In Michigan, the Saginaw Lobe left behind high-relief moraines and drumlin fields that shaped local drainage and soil patterns for millennia to come.³ As the ice disappeared, the bare ground it revealed was colonized first by tundra-like vegetation, then by spruce forest, and eventually, as the climate continued warming and drying, by the grasslands and mixed woodlands that would define the region for thousands of years.

How Prairie and Forest Divided the Region

The Midwest was never all one thing. A persistent boundary between prairie to the west and forest to the east ran roughly through the middle of the region, but it was not a fixed line. It wandered east and west over thousands of years in response to shifts in temperature and precipitation. Pollen records from lake sediments in Iowa, Wisconsin, and Minnesota allow researchers to track these movements in surprising detail.

Prairie began invading what is now southeastern Minnesota from the west around 8,000 to 9,000 years ago, but its eastward expansion then stalled for about 2,000 years while mesic forest held on less than 100 kilometers to the east.⁴ Across a broader transect from central Iowa to southeastern Wisconsin, prairie dominated central Iowa and the climate was drier than today from roughly 8,000 to 3,000 years ago. During the driest interval, around 6,500 to 5,500 years ago, conditions in central Iowa were parched, but eastern Iowa and Wisconsin remained relatively wet with mesic forests still intact. Prairie eventually pushed into eastern Iowa around 5,400 years ago but did not penetrate much farther east; instead, the forests of southern Wisconsin and northern Illinois shifted from mesic hardwoods to drier oak-dominated woods.⁵

The result, by the time Europeans arrived, was a gradient. Western Minnesota and western Illinois were widespread prairie with scattered oaks, averaging fewer than 50 trees per hectare and around 40 metric tons of biomass per hectare. Southern Wisconsin was predominantly savanna, with up to about 100 trees per hectare. Moving east into Indiana, forest structure thickened dramatically, and pockets of mixed mesophytic forest in eastern Indiana reached as much as 600 metric tons of biomass per hectare at the township scale.⁶ That is an enormous range of density, from open grassland with a few lonely bur oaks to forest as thick as anything in the Appalachians.

The Prairie Itself

Standing in the tallgrass prairie before it was plowed would have been disorienting. Big bluestem, Indian grass, and switchgrass could reach well above a person’s head by late summer, creating a sea of vegetation that obscured the horizon. But the real mass of a prairie was hidden underground. In a central Missouri prairie, researchers measured root systems down to a 34-inch profile and found between roughly 1,450 and 1,900 grams of root material per square meter, depending on the season. Over 80 percent of that root mass was packed into the top 10 inches of soil.⁷ This dense root network built the deep, black, carbon-rich topsoil that would later make the Midwest the most productive farmland on the planet. The roots were the prairie’s engine, cycling nutrients, holding moisture, and feeding a vast underground community of fungi and microbes.

That underground community was itself remarkable. Tallgrass prairies supported diverse communities of arbuscular mycorrhizal fungi, organisms that form symbiotic partnerships with plant roots to exchange nutrients. Modern comparisons between remnant prairies and adjacent agricultural fields show that spore density in prairie soils is more than twice that of farmed land, and species richness of these fungi is nearly three times higher. Disturbance-sensitive fungal families, largely lost from cropland, thrive in prairie soil at levels three to nearly five times those found in agricultural fields.⁸ These fungi were not a footnote to the prairie ecosystem; they were part of its architecture.

Oak Savannas and the In-Between Spaces

Between the open prairie and the closed forest lay the savanna, one of the Midwest’s most distinctive and now rarest ecosystems. Savannas were open woodlands dominated by fire-tolerant oaks, with a grassy understory that blended prairie and forest species. In northeast Iowa, presettlement vegetation included a mosaic of wet meadows and riparian shrubs on the floodplains with oak savanna climbing the valley walls and spreading across the uplands.⁹

Savannas were maintained by frequent fire, but the precise disturbance dynamics varied by landscape position. Historical vegetation reconstructions of Midwestern savannas have found differences between upland and lowland types, with no evidence that lowland savannas depended on flooding. Instead, the uneven-aged canopy structure of lowland savannas suggests periodic disturbance of another kind, likely fire, kept them open.¹⁰ Without regular burning, savannas would have gradually thickened into closed-canopy forest. This makes the savanna one of the best examples of a Midwestern landscape that required active disturbance to exist at all.

Wetlands and the Prairie Pothole Region

The pre-farming Midwest was extraordinarily wet in ways that are hard to appreciate today. Glacial retreat left behind millions of small depressions, particularly across what is now the Dakotas, Minnesota, and Iowa, that filled with water seasonally or permanently. These prairie potholes formed one of the most important wetland complexes on the continent, providing breeding habitat for vast populations of migratory waterfowl and supporting aquatic invertebrates, amphibians, and a web of life that extended into the surrounding grasslands.

Since European settlement, roughly 90 percent of the area of these depressional wetlands has been lost, mostly to drainage for agriculture. But the damage was not evenly distributed. Smaller wetlands were preferentially destroyed, fundamentally altering the historical relationship between wetland size and frequency and homogenizing what had been a highly varied patchwork of large and tiny water bodies.¹¹ The pre-farming landscape would have had a far more textured hydrology: thousands of small, ephemeral pools alongside larger marshes and sloughs, all connected by seasonal overflows and shallow groundwater.

Farther south, the Grand Prairie of central Illinois was one of the Midwest’s largest wet prairies, a vast expanse of waterlogged grassland that resisted settlement until drainage tile technology made it feasible to farm. In just a few decades, this landscape of saturated soils and slow-moving water was transformed into straightened streams and drained fields, opening up some of the world’s richest agricultural soils but destroying the prairie hydrology in the process.

Fire and the People Who Set It

The tallgrass prairie was not simply a product of climate. It was maintained by fire, and the primary source of that fire was people. A detailed review of written accounts from the Midwestern tallgrass prairie between 1673 and 1905 found that Native American ignitions far outnumbered lightning ignitions. The researchers concluded that Indigenous burning should be considered the primary force behind the origin and maintenance of these grasslands.¹² When Native American use of fire declined in the early nineteenth century, observers noticed a rapid growth of trees on former prairie and barren sites, likely from well-established root systems that had been repeatedly top-killed by fires but sprang back once the burning stopped.

This was not accidental. Indigenous peoples burned strategically to maintain open habitat for hunting, to encourage the growth of food-producing plants, and to manage the landscape at a regional scale. The effects went well beyond grasslands. Researchers have argued that Native American land-use practices, especially regular burning, had a profound influence on the entire historical development of the eastern oak and pine forests, savannas, and tallgrass prairies. Without sustained burning, drier prairie and open woodland would have converted to closed-canopy forest, and fire-tolerant mast trees like oaks would have been replaced by shade-tolerant species that produce far less food for both humans and wildlife.¹³

In other words, the “natural” landscape that European settlers encountered was already the product of thousands of years of deliberate management. The boundary between prairie and forest, the dominance of oaks in the transition zone, the productivity of nut-bearing trees, all were influenced by human activity long before the plow arrived.

Indigenous Agriculture Was Already There

The idea that the Midwest was purely a hunting-and-gathering landscape before European contact is wrong. By at least 3,800 years ago, Indigenous peoples in the river valleys of eastern North America were cultivating a coherent crop complex that included domesticated bottle gourd, marshelder, sunflower, and two varieties of chenopod, along with possible cultivation of squash and little barley.¹⁴ This was not a sudden shift to farming but rather an expansion and enhancement of existing ways of life centered on resource-rich river valleys.

Recent work has pushed the evidence of intensive agriculture even further. In Michigan’s Upper Peninsula, LIDAR surveys and excavations have uncovered densely clustered raised garden bed ridges covering a far greater area than previously recognized, created by ancestral Menominee communities near the northern limits of maize agriculture. The findings suggest that the precolonial landscape was more shaped by human hands than researchers had realized.¹⁵ These were not patches of occasional gardening. They were substantial, deliberate transformations of the land surface.

The crops themselves were remarkably diverse. The methods of ancient Indigenous farmers combined food production with biodiversity in ways that modern agriculture does not. Some researchers have pointed out that cultivating wetland- or floodplain-adapted crops, as Indigenous farmers did, could offer a practical model for parts of the Midwest where flooding is becoming increasingly severe and unpredictable.¹⁶

The Wildlife That Shaped the Land

Bison were ecological engineers of the tallgrass prairie. Their grazing patterns created a patchy landscape of closely cropped areas and tall, ungrazed stands, which in turn created habitat variety for a wide range of plants and animals. Long-term research comparing bison-grazed and cattle-grazed tallgrass prairie at Konza Prairie in Kansas has shown that bison grazing increases plant species richness at both small and large spatial scales in ways that cattle grazing does not match. Bison-grazed plots accumulated more annual and perennial forb species over time, and they left less standing grass biomass at the end of the grazing season, creating the structural patchiness that defines healthy tallgrass prairie.¹⁷

Another vanished ecological force was the passenger pigeon, once so abundant that migrating flocks darkened the sky for hours. These birds were primarily seed predators, consuming enormous quantities of acorns, beechnuts, and chestnuts, but they also contributed to seed dispersal. Their nomadic habits and capacity for delayed digestion meant they could move seeds across long distances and habitat discontinuities, potentially playing a role in the surprisingly rapid northward migration of nut trees after the glaciers retreated.¹⁸ Experimental work on passenger pigeon diets has confirmed their role as seed predators while also identifying physical limits on their gape size that would have restricted which tree species they could actually disperse.¹⁹ With the passenger pigeon extinct since 1914, and bison reduced from tens of millions to a handful of managed herds, two of the forces that actively sculpted the pre-farming Midwest are simply gone.

Streams and Freshwater Life Before the Plow

The Midwest’s rivers and streams supported an extraordinary diversity of freshwater mussels, a group of organisms that is easy to overlook but was ecologically important as water filterers and as food for wildlife and Indigenous peoples. Even before European settlement, however, this community was already showing signs of human impact. The relative abundance of mussel species in the genus Epioblasma declined steadily over thousands of years, a trend that could reflect either human disturbance or long-term climate change. But the rate of decline increased significantly after the advent of large-scale maize agriculture in the southeastern United States about 1,000 years ago, suggesting that prehistoric land-use activities were already altering freshwater communities in ways that foreshadowed the much larger changes to come.²⁰

This is an important corrective to the common image of the pre-farming Midwest as ecologically pristine. Indigenous peoples changed the landscape and its waterways, just at a lower magnitude and slower pace than what came after European settlement. The direction of change, more sedimentation, more disturbance to stream habitats, was similar; the scale was not.

What the Prairies Left Behind in the Soil

Even after more than a century of industrial agriculture, the Midwest’s soils still carry a signature of the prairie that built them. Remnant tallgrass prairie sites in Nebraska have been used as benchmarks for soil health, providing reference profiles against which degraded agricultural soils can be measured. The suite of physical, chemical, and biological properties in prairie soil reflects millennia of root growth, fungal networks, and organic matter accumulation, processes that agriculture interrupts but does not entirely erase.²¹

Prairie restoration can partially recover what was lost. Restorations that use repeated seeding events from large species pools achieve plant diversity levels comparable to undisturbed reference sites, while single-seeding efforts tend to resemble already-disturbed remnants.²² The underground fungal communities also rebound: restored prairies show spore densities more than double those of farm fields and significantly higher diversity of disturbance-sensitive fungi.⁸ But “recovering” is not the same as “recovered.” The difference between a restored prairie and an ancient remnant is measurable, and the centuries of root growth and organic matter accumulation that created the original soils cannot be replicated on a human timescale.

Prairie Pollinators and the Seasonal Rhythm

The pre-farming Midwest offered pollinators something modern agriculture does not: continuous floral resources from spring through fall. Native tallgrass prairie plants bloom in a staggered sequence, with different species flowering in each month, creating an unbroken supply of pollen and nectar. Research tracking the pollen sources of managed honey bees placed near prairie remnants found that native plants became the dominant pollen source in August and September, outpacing nonnative species that provided most of the pollen earlier in the summer.²³ In a landscape dominated by row crops, that late-season bloom is largely absent. Before farming, it would have sustained not just bees but an entire community of butterflies, beetles, flies, and other insects that depended on flowers through the end of the growing season.

The seasonal rhythm of the prairie extended to water cycling as well. Native prairies move more water into the atmosphere through evapotranspiration than cropland does, partly because their growing season is longer. In the central Mississippi River basin, prairie evapotranspiration runs about 69 millimeters per year higher than cropland, an 11 percent difference driven by the prairie’s extended period of active growth. Before the land was converted, this meant more moisture cycling locally, cooler surface temperatures during the growing season, and a different pattern of rainfall recharge than what the tiled, drained agricultural landscape produces today.