Even by 19th century standards, our fair city was a life-sized petri dish of disease. Suffering from poor sanitation and infected public wells, cholera ran rampant through the shantytowns on the waterfront, including what is now known as Market Square. Death came quickly, often within hours of the first symptoms, and hundreds of bodies were hastily disposed of in shallow, mass graves at Potter's Field. Potter's Field was closed in 1855, after the epidemics. Sometime in the 1870s, most of the bodies were relocated to either the Necropolis cemetary overlooking the Don River Valley or Mount Pleasant Cemetery.
Problem is, records for that time are scarce.
Although it's probably true that all the marked graves were moved, there is little evidence by way of records to prove the relocation of the mass graves. And to cast further doubt on what really happened, human remains were discovered at Yonge and Bloor Streets in 1929. Lacking any marker or identification, the remains were soon re-interred at another location. The rest of the story is lost to the decaying effect of time. All we really know is that we don't know much about the current whereabouts of those unfortunate souls.