It would be impossible to know without an image
but it may be one of the ferns on the list at the site below. Possibly Virginia Chain Fern?????????
Check the list and then google the image of each until you have gone through them all.

Here is a link that might be useful: PA plants used for roadside plantings

I would suggest either Ostrich fern or New York fern. Both of them are pretty good spreaders.

Linda, If you are going to be pulling it like weeds, I'd love to have your weeds for a woodland area I'm trying to create in suburban DC. Would be happy to pay postage!

My Guess it a New York fern..Ostrich ferns spread,but a lot slower than the New York fern and you can easily identify the Ostrich with its nobby center and is symetrical in growth.I had just a single New York about 3-4 years ago and now they have spread all over. So now I keep them only in a selected area away from the other ferns..Tom in NWPA

Would a New York fern be hardy in Illinois?

I'm looking for exactly what he is having a problem with. Something that naturalizes fast - spreads - loves shade - but of course, can go through an Illinois winter.

I look around and no one seems to have ferns. The plant places all have "delicates" that can't survive outside. My ostriches died.

I'm not looking for delicate - like infrared - I'm trying to create a woodland here under some very mature trees.

According to the USDA plant site, Thelypteris noveboracensis (new york fern) is natrually found in Illinois (but only a few counties, click on the state to see where).

Not many plants sell the "common" ferns, you might have to get a start from someone. Try contacting your local native plant society for sources of native ferns.

Here is a link that might be useful: Distribution map

Thank you esh - I will. Appreciate that.

technodweeb, you should not have any problem having them ( New York ferns )winter over,we get the same weather as Chicago and they spread very well here in North West Pennsylvania in the snow belt portion , now.....they are not evergreen ,so they Will die back to the surface and they will just about double or tripple in number the following year.At least thats what they have done here. However, and as I mentioned at the very first sign of frost they start to die back in the late fall...Tom