village, Cook county, northeastern Illinois, U.S. A residential suburb of Chicago, River Forest lies on the Des Plaines River, about 12 miles (19 km) west of the city's downtown. A sawmill built on the riverbank in 1831 drew settlers to the area. The community was temporarily known as Thatcher for David C. Thatcher, an influential early settler. The village was laid out after the arrival of the railroad in 1865. River Forest is the seat of Dominican University (1901) and Concordia University (1864). It has several buildings designed by Frank Lloyd Wright (Wright, Frank Lloyd), including the Winslow House (1893) and the River Forest Tennis Club (1906). Inc. 1880. Pop. (1990) 11,669; (2000) 11,635.