Police say that at around 10:30 a.m., rescue crews responded to the Housatonic River for the report of a person in the water.
Upon arrival, a man was found sitting at the base of a pillar for the railroad bridge.
It was later determined that he had fallen off of the bridge and into the water on Sunday night and then swam onto the bridge base.
The Fire Chief says that the man suffered a leg injury in the fall but that there was no word on frostbite.
The man was safely brought to shore and taken to Yale New Haven Hospital for treatment. His identity and current condition are unknown at this time.
Officials say that three people who performed the rescue were also taken to Griffin Hospital for an evaluation for cold exposure.