I've looked over the pictures for several key areas, and found them very interesting.
First, I located Bartlett. After a bit of poking around on two pictures, I was able to locate my neighborhood. In 1938 (when the picture was taken) where my nice suburban neighborhood would rise in about 40 years was taken up with large open farm fields. I could spot a couple of farm houses off of Devon road in between the two very small towns of Bartlett and Ontarioville. While Bartlett was clearly bigger, it still was very small then. (Ontarioville ceased to exist as a separate town at some point, and is now the neighborhood around the Hanover Park train station, and would be hardly remembered if it wasn't for the name of the road that intersects County Farm before becoming the next incarnation of Devon).
Next I looked around Palatine and Arlington Heights. I was able to spot Staples Corner (Rand and Dundee) and was able to determine that nearly everywhere I lived in Palatine, and where I work in Arlington Heights were more farm fields. I did confirm that Palatine was a much bigger town then Bartlett in 1938 or 1939. I don't think I ever located Arlington Heights (the pictured aren't seamed like in Google Maps, so you have to manually move from picture to picture). I did, however, notices that Arlington International Racecourse (or whatever it was called at the time) was there, but surrounded by more farms.
Finally, I took a look at Wheaton. Wheaton itself was not that different from today -- at least near Downtown. However, where we lived for a few years near Roosevelt and County Farm was, you guessed it, more farm fields.
Although I knew it already, it was amazing to learn that in less than a century all of these farm fields would become built up suburbs, with only a few small tracts of farming left. Of course, when I first moved to the Chicago area, many of my parent's friends and acquaintances who grew up in the Chicago area not too long after these pictures were taken, would laugh when they heard I was complaining about how suburban and built up Palatine and Arlington Heights were, since these people remembered them as small farm towns on or just past the edge of the metro area.