Agriculture on the American Great Plains has been constrained historically by water scarcity. In the latter half of the 20th century, technological improvements enabled farmers over the Ogallala aquifer to extract groundwater for large-scale irrigation. Comparing counties over the Ogallala with nearby similar counties, groundwater access increased agricultural land values and initially reduced the impact of droughts. Over time, land-use adjusted toward high-value water-intensive crops and drought-sensitivity increased. Farmers in nearby water-scarce counties have adopted lower-value drought- resistant practices that fully mitigate their naturally higher drought-sensitivity. The historically evolving impact of the Ogallala aquifer illustrates the importance of water for agricultural production, but also the large scope for agricultural adaptation to groundwater and drought.