The Rockford airport/RFD obs site has seen significant development and paving over the past 10 years as it has grown to one of the largest cargo airports in the US and for a few recent years the fastest growing cargo airport in the world. It's also UPS's #2 hub and one of Amazon's larger air hubs. Several large maintenance/rebuild/overhaul operators have built large hangers and pads as well.
Outside of the airport actually development in the RFD region has been minimal since the financial crisis. But of course the actual obs site itself is probably holding on to a fair bit more heat than in the past given many more paved acres in recent years.
(I'm luckyweather, the board's rockford region regular. for some reason when I log in to the board in a browser it has my old screenname, vs same login on tapatalk on mobile, some tapatalk weirdness BS. whatevs.)