In Toledo, The Purple Gang came down from Detroit. Licovetti the notorius Mob boss ran a few Illegal casino (Clubs). To name a few of the Toledo big Clubs:

Hollywood Club
Maumee Club
Dixie Inn

I have been reading the book: "Unholy Toledo" which mentions a few of the clubs. Unfortunately the book is very sparce and doiesnt deal well with places. Its more into specific events. But still a few places have been mentioned and of course Licovetti.

As Gene mentioned, Ohio, KY and IN were the most prolific for casinos. As far as what I have read, Toledo was considered THE most prolific and in second place was Covington , KY. Chicago of course was a biggie as was a large number of casinos in Indiana.

There are a number of books out on the illegal casinos in different areas. For a good insight into the casinos in the Covington area, you may want to talk to Gene Trimble. Rumor has it that he knows quite abit about them.