Brookfield. 1 Village (1990 pop. 18,876), Cook co., NE Ill., a residential suburb of Chicago; inc. 1893. The noted Chicago Zoological Park (Brookfield Zoo) is there. 2 City (1990 pop. 35,184), Waukesha co., SE Wis., a suburb of Milwaukee; inc. 1954. With its iron foundries and light manufacturing, the city has undergone suburban expansion since 1975.