When studying history it's a slippery slope you take when trying to compare a modern place or thing to the past. You can't compare a prior bankrupt city to Detroit for several reasons. The main reason being that Detroit's bankruptcy is closely tied to the auto industry. There was a very good discussion about this recently on AskHistorians. The auto industry, as it was known in Detroit, began with Henry Ford's assembly line in 1913^1. If you wanted to compare a prior "motor" city to Detroit that would be a more appropriate question, but Detroit was the first. She's unprecedented. But if you were to compare previously bankrupted cities to those of today, you wouldn't want to look any further than 1934 when "the the Bankruptcy Act was amended to extend to municipalities,"^2 known as Chapter 9, Title 11, of the United States Bankruptcy Code. According to this article, "of more than 55,000 municipal entities, fewer than 600 have filed for bankruptcy protection since 1937."
Detroit is not the only city in the US [going] bankrupt. Just perhaps the most well-known and the hardest to fall. This article gives an interesting look at other cities struggling with debt and bankruptcy.