Horned Grebe?

I took this image on March 31 in Crest Hill, IL. Is this a Horned Grebe with winter plumage?

I would say you nailed it! Looks a bit overexposed due to harsh lighting, but great "find" here in the MidWest...

Yes, starting to molt into breeding plumage.

Agree. Note: horned typically shows the butt low to the water as here. Eared usually has the high butt look.