Off of Trax Records, one of the original Chicago house labels. Their entire catalog has just recently been digitized, and is available mostly on uk sites such as boomkat and bleep. 14 Tracks (a boomkat service) has a great sampler of the Trax catalog that is worth a listen. This version is a previously unreleased version that is actually a lot more interesting than the original release (at least to me), but you can judge for youself. Here is the original:
