Illinois Salines along the Saline River in southern Illinois was a major salt source for Indigenous communities from at least the Early Woodland through the Mississippian period, with its salt traded widely across the region. The site is especially important archaeologically for preserved organic remains and discoveries such as large pottery vessels formed in baskets, leaving woven impressions. After American settlement, the salines became the first major industry in Illinois Territory, and their profitability led to state ownership in 1818. Their operation also exposed a stark contradiction: slavery and later indentured servitude were allowed there despite Illinois entering the Union as a free state. Production continued until 1870.