So I decided to take a few inside and do some Googling. Google had the answer to my question (OF COURSE) and much more. I found this page about wild onions which said: "Wild onion (A. validum or A. canadense) is a bulbous herb of the Amaryllis family and is a close relative of cultivated onion (Allium cepa L.). It has a distinct onion odor. It has slender grass-like leaves and reaches about 2 feet in height when flowers appear in late summer. Leaves are narrow, long, and with parallel edges arising from the small underground bulb."
Distinct onion odor? Check.
Slender grass-like leaves about 2 feet in height? Check.
Then the site went on to suggest that Chicago derived its name from wild onions: "Indians, mainly Potawatomi, who were the most powerful tribe around the south end of Lake Michigan, hunted, traded furs, and occasionally camped in the area they called "Checagou," evidently referring to the garlic wild onion smell which permeated the air." Some Illinois trivia, brought to you by my backyard.
I verified that these wild onions were edible (though very pungent), and I decided to make a wild onion pesto. First I had to pick all the remaining wild onions I could find - of which there were many:
Then I had to clean them...which took way too long.
Then came the pesto making. I chopped up the green onions, and processed them with 1 clove garlic (which was totally unnecessary because those onions had more than enough allium punch themselves), pine nuts, parmesan, olive oil, salt/pepper, and lots and lots of lemon juice to cut the pungency of the wild onions.
I divided up the pesto into four portions and froze them. I used one for a pesto pasta salad last month, and it definitely tastes like a "wild" onion pesto. Perhaps I should've used less of the bulb? Either way, it was a fun discovery and (day-long) experimental project.