Soils

Archeological excavation reveals dark soil and red brick at Lincoln Home National Historic Site.

NPS/Lincoln Home National Historic Site

The Lincoln Home was built on the Grand Prairie region that covered 90% of central Illinois prior to European settlement. The black soil of the Grand Prairie supported a rich display of grasses and wildflowers that grew upwards of 8 feet tall in this relatively flat area. Big bluestem (Andropogon gerardii), Indian grass (Sorghastrum nutans), and compass plant (Silphium laciniatum) thrived in this climate and soil.

The black soil of this region formed when the most recent glacial episodes (Illinoisan and Wisconsonian, ca. 150,000 – 50,000 years ago) deposited glacial drift in the flat landscape. These rich mesic soils endured scorching summer heat, intense spring rains, lightning fires, and freezing temperatures. The extensive array of grasses and forbs that grew on the land were able to withstand these diverse weather conditions. Over time, this soil became rich and productive, and prairie plants became anchored through deep root systems.

In the 1830s, settlers began converting the Grand Prairie into farmland with the help of the moldboard plow (invented in 1837). Agricultural communities replaced the native tallgrass prairie and farmers planted corn and soybeans. The Lincoln Home was built on these plowed and disturbed soils.

Today, the buildings and landscape of Lincoln Home National Historic Site model Springfield of the 1860s. There are signs of prairie vegetation on site, like wild strawberry (Fragaria virginiana) and bur oak (Quercus macrocarpa), but the Grand Prairie's soil is no longer visible as visitors walk the tree-lined streets of the Lincoln Home and neighborhood.