We report the long-distance dispersal of a subadult male cougar (Puma concolor) from South Dakota to Milford, Connecticut, where it was struck and killed by a vehicle. Genetic samples suggest this animal originated from the Black Hills of South Dakota while isotope analysis and physical inspection revealed no evidence that the animal had been held in captivity. We detected this dispersing individual at 5 locations along its route (Minnesota, 3 times in Wisconsin and New York) with DNA from fecal or hair samples, and with multiple photographs from citizenrun camera traps (3 in Wisconsin and 1 in Michigan). The > 2,450 km straight-line distance (Black Hills of South Dakota to Connecticut) traveled by the cougar is the longest dispersal documented for the species. We propose a likely route of > 2,700 km over 2 years based on topography and our confirmed records. We suggest that this excessive movement was motivated by the absence of female cougars along the route. The documentation of such a rare biological event not only shows the great dispersal potential for male cougars but also highlights our ability to detect these movements with verifiable voucher DNA and photographic records. Evidence collected for this one animal, and complete absence of verifiable data from most anecdotal reports of cougars in the east, further confirms the lack of a breeding population in the region.