I ran into a similar situation where a husband abandonded a wife & child in New Brunswick, Canada & showed up later with a new wife in the US. I think it was even in Cook County, IL. My case was in the late 1800's, earlier than yours.The divorce was granted in 1895. To get a divorce in Canada required an act of parliament. As far as I know the Canadaian divorces are not indexed anywhere for the time span of interest to you; the indexing ended around 1919 last time I looked. I'd start by finding a kind volunteer or paying a researcher in the Chicago area to search through Cook County divorce records circa 1922-1930. If they find that your fellow applied for a divorce there, you will be spared the agony of trying to find a Canadian divorce record. It turns out that's where my Canadian gentleman got his divorce. His ex-wife never left Canada during the whole process. I was even able to request a transcript of the divorce case from a court in Cook County, once a kind stranger helped me figure out what the divorce date was & what court was used. Also, you should take a look around the Internet for a Cook County Court system website that might just show whether any indexing exists for divorce cases circa the 1920's. You might get lucky & be able to search an index, or find someone in the area who can search for you.