I didn't really know anything about Illinois Speed Press other than Paul Cotton was from that band before he went to Poco (one of my FAVORITE bands!). Didn't know at all about Bonnie B coming from Illinois at all either, thanks!
I was thinking of some others, and there was a story goin' round about Silver Bullet, another "Blytham band*". My understanding was that Bob Seeger hired the Silver Bullet band to back him up, and then started replacing people. Don't know if that's true or not.
Also a local radio station used to play some recordings by a Peoria band called Suburban Nine to Five. One was a cover of a Buffalo Springfield song. The band included Gary Ricrath and Dan Fogelberg.
I'd also forgotten a really important artist from the area. Luther Allison was from Peoria and I was able to see him a LOT just as I was starting to play bass. A friend of mine was a very good guitarist who jammed with Luther a lot. Luther offered Jeff a gig in his band, but the money wasn't enough to make up for the travel...
*The Blytham Agency was a Champaign/Urbana based booking agency that handled a lot of band working around Illinois. They had a circuit of college-town bars they'd book rock bands in to and seemingly had the rare ability to give you decent bookings in a logical order instead of sending the band to Rockford then south to Springfield, then back north to Bloomington, then south again to Jacksonville. They'd try to work the band so they weren't driving back and forth. The local bar that worked with them, the Red Lion Inn, was where I saw Cheap Trick (Rockford guys, the owner of the guitar store I managed grew up with them and knew Rick from when they started playing guitar at the age of 10). There were some other bands I've wondered where they or the people in them went on to.
Groups like A Full Moon Consort who'd do covers either dead-on exactly like the record, or totally reinvent them. I heard four different versions of Joni Mitchel's "Raised On Robbery" by AFMC in a two month period, just amazing musicians.