Curse of Kaskaskia
The story goes that in the late 18th century, a local Indian fell in love with the a rich fur trader's daughter, Marie. Marie's father didn't want her to marry a red man, therefore he let the Indian be tied to a log and sent off down the Mississippi river to die. Before the Indian died, he swore a curse. Bernard, the father would be dead, the Indian and Marie would be together, and the land of Kaskaskia (who was then the top spot for trading goods in Illinois) ruined. Furthermore, the curse included that all the churches would be destroyed and the dead would rise from their graves.
A year later, Bernard and Marie both died. Over the next 100 years the Mississippi shifted its course and flooded the town, until it became totally cut off from the main land. The cemetery was washed away by the floods, taking the corpses into the river. In 1973 the church and altar were flooded. BoM,p.33-34
In 2000, all of 9 people still lived in Kaskaskia (Source and further reading on Wikipedia).