Sorry. I was hoping you would find Louisa living next door or just down the block, with her parents!

If you can find them in the 1900 census, it will give the month and year of their birth, and also the year of immigration and whether or not Thomas was a naturalized citizen. That would give you a little more to go on when you are trying to identify him through IOM baptisms.

Most likely, at least in the first generation, they were Methodist or Church of England (Episcopal), and a reference librarian in Chicago may be able to help you identify a church in the area where they lived.

Also, I would certainly look for the children's marriages, and follow up on any other information about the children that you may have.