Elmhurst is a city mostly in DuPage County and overlapping into Cook County in the U.S. state of Illinois, and a western suburb of Chicago. …Elmhurst is a city mostly in DuPage County and overlapping into Cook County in the U.S. state of Illinois, and a western suburb of Chicago. Members of the Potawatomi Native American people, who settled along Salt Creek just south of where the city would develop, are the earliest known settlers of the Elmhurst area. Around 1836, European-American immigrants settled on tracts of land along the same creek. At what would become Elmhurst City Centre, a native of Ohio named Gerry Bates established a community on a tract of "treeless land" in 1842.