Hamilton is still known as little Chicago, although it is now just a drug infested shit hole, that some folks call home.
Cleveland is nicknamed "Little Chicago" or "Lil Chicago" because of it's many similarities to Chicago, but everything is just on a smaller scale. The demographics and trends for both areas are very similar. Fads and styles that start in Cleveland will quickly spread to Chicago and vice versa since the cities are relatively close and very connected.
The nickname has been around since the early-mid 1900s when Cleveland was at one time the 5th largest city in the country and rivaled Chicago but was just slightly smaller. People started noticing the striking similarities between the two big cities. Cleveland also had a huge mafia presence like Chicago and the Cleveland and Chicago mafia families were allies for a long time.