Looking to identify this plant in Chicago.

It has the center of an Asteraceae with 5 very tiny white petals that are radial. each petal has 3 tiny lobes. leaves form where stem splits. Creeps/spreads like a chickweed.

Any ideas?

Not chickweed, but I don't know what it is. I have seen it before but...

What butterflies does it attract?
I feel like I've seen it around too...
Would help if you posted some pics of the plant actively growing.

The flowers kinda look like bidens and galinsoga.

Not having any luck matching the foliage...

Or... Maybe check this page:

http://www.hippocampus-bildarc...

I'm thinking Galinsoga ciliata also.

Let's ask @LysmachiaMoon !
Apparently she has a ton of galinsoga.

Does Gallant Soldier (Galinsoga parviflora) grow in Illinois?

My first thought was maybe False Daisy (Eclipta prostrata) but upon looking at more photos I think it does mostly resemble Galinsoga. This page says that Galinsoga parviflora is occasional in the north 1/2 of Illinois. https://books.google.com/books...

This page mentions Jackson County and Champaign County: https://books.google.com/books...

plantladylin said:Does Gallant Soldier (Galinsoga parviflora) grow in Illinois?

Yes, but is not as common there as G. ciliata according to this Illinois wildflower page:

http://www.illinoiswildflowers...

(Note they give G. ciliata as a synonym for G. quadriradiata).

According my field guide G. parviflora has nearly hairless stems and has shorter rays than G. ciliata. The link above gives some other differentiating features.