Eastern cougars once roamed every U.S. state east of the Mississippi, but it has been eight decades since the last confirmed sighting of the animal. Now, the U.S. Fish and Wildlife Service has officially declared the subspecies extinct and removed it from the U.S. endangered species list.

The decision, announced Monday, is the result of years of deliberation. The agency conducted an extensive review of the eastern cougar in 2011, and recommended it be removed from the endangered and threatened species list in 2015, Reuters reported. The species, also known as pumas, are the genetic cousins of mountain lions in the Western United States and of Florida panthers, which are now found only in the Everglades.

There is “no evidence of the existence of either an extant reproducing population or any individuals of the eastern puma subspecies,” the announcement in the Federal Register said. “It is also highly unlikely that an eastern puma population could remain undetected since the last confirmed sighting in 1938.”

Cougars were common throughout eastern North America until the late 1800s, when their populations began to drastically decline as forests and prey disappeared and European settlers killed them to protect their livestock and families, according to the FWS.

Conservation groups said the decision clears the way for eastern states to rebuild cougar populations in habitats such as the Adirondacks and White Mountains using mountain lions from the U.S. West. Western mountain lions are confirmed to have occasionally ventured as far east as Connecticut, with reported sightings even further in Maine.

Eastern states “need large carnivores like cougars to keep the wild food web healthy,” Michael Robinson, a conservation advocate at the Center for Biological Diversity, said in a statement. “[They] would curb deer overpopulation and tick-borne diseases that threaten human health.”