From your photo, it looks like an ash tree, but it's not close enough to tell. Other possibility is a hickory maybe? Same with the disease issue. Too hard to tell from the photo. But, if it is an ash tree, it's probably Ash Anthracnose. It's warm and very wet in Chicago this year, right? Perfect conditions for this: "Ash anthracnose is probably the most common disease of green ash. It is caused by a fungus and occurs during cool, rainy weather. It can be confused with ash plant bug and herbicide damage. Individual trees vary in their susceptibility to anthracnose to the extent that some trees may be infected every year and others only rarely or never at all. Initial symptoms on green ash include very small (grain of sand-sized) purple or brown spots, sometimes with a cream-colored center, on young leaves. These spots may enlarge and coalesce forming brown blotches. Leaves often become distorted and drop and young shoots may be killed. Defoliation and leaf browning cause homeowners a great deal of concern, but treatment is generally not warranted. Affected trees usually put out a second flush of leaves and make up for lost time later in the growing season. However, trees that have been defoliated three to five years in a row might benefit from chlorothalonil, mancozeb or thiophanate treatment at budbreak to prevent infection. The fungus can overwinter on the ground in infected leaves and twigs, so raking and disposing infected material may help reduce infection the following spring." Your main link didn't work for me -- brought up a screen, but no photos, looks like you have to create an account to view them, and I didn't want to do that. Here is a link that might be useful: Pamphlet where I got the Ash Anthracnose info:

Check out Robinsonella cordata, with gorgeous blue hibiscus-like flowers. I just picked one up at the UC Berkeley Botanic Garden fall sale, and am anticipating the first time I get to see it bloom. I am also enjoying the fall blooms on my Cunnonia capensis tree in my front garden, but this is another rarer tree species that takes some searching to find. The Chinese Fringe tree is also quite nice or how about Cornus capitata?.

Agree w/Bill. Bigtooth aspen not uncommon in NJ hills, but trembling aspen rare/absent. In fact I saw catkins on a bigtooth aspen here just a day or so ago.

Brachychiton