All seven of the IL communities listed in the top 100 here are in the SW suburbs (Will, Kendall, Kane Cos.) They are the natural expansion of residences for the jobs in the SW communities of Aurora, Naperville, Downers Grove and Oak Brook (and others primarily in Du Page Co.) where housing has become too expensive.
But for these towns to be among the 100 fastest growing in the nation, there must be other factors at play. There must be very low unemployment or some type of industry there that is doing well.
DuPage seems similar to Nassau County, NY. It has a small land area, is densely populated (by suburban standards), its an inner suburb that has no room left to expand, and is trending Democrat.
The proposed airport is actually quite a bit east of the high growth area. However it would create a new job area accessible the the relatively poor and increasingly African American communities in south Cook. The airport would not replace O'Hare, but augment it, much like Newark augmented JFK and LaGuardia in NYC when it was upgraded in the 80s.
Well I wish they would just go ahead and build it. They seem to have been arguing about it for years. IIRC, the alternative was to build a new airport in Gary but I can understand why people would want to avoid that area. (Very High Crime).
