This is a database of stealth journalism including investigations of finances, the Klan, mental hospitals, etc. It is historical and includes old and more recent stories. In their About section, they say:

This collaboration with NYU Libraries collects many decades of high-impact, sometimes controversial, mostly U.S.-generated journalism that used undercover techniques. It grows out of the research for Undercover Reporting: The Truth About Deception (Northwestern University Press, 2012), which argues that much of the valuable journalism since before the U.S. Civil War has emerged from investigations that employed subterfuge to expose wrong. It asserts that undercover work, though sometimes criticized as deceptive or unethical, embodies a central tenet of good reporting–to extract significant information or expose hard-to-penetrate institutions or social situations that deserve the public’s attention. The site, designed as a resource for scholars, student researchers and journalists, collects some of the best investigative work going back almost two centuries.

I checked for a big undercover story from Chicago, the Mirage Bar corrupt inspectors story and it is there.