The 2-1/2-year-old male wolf was tracked Thursday using a GPS collar as it crossed the Oregon border into California's Siskiyou County, the San Francisco Chronicle reported.
Environmentalists said they were pleased to see the endangered species back in California, a sentiment not shared by Northern California ranchers worried that recolonization could endanger their livestock.
"Whether one is for it or against it, the entry of this lone wolf into California is a historic event and the result of much work by the wildlife agencies in the West," Charlton H. Bonham, director of the California Department of Fish and Game, said. "If the gray wolf does establish a population in California, there will be much more work to do here."
There's no guarantee the lone wolf will remain in California, experts said.
He'll have to wait a long time before a female wolf also discovers the Golden State, they said.
"He's looking for a pack or other mates," Mike Fris with the U.S. Fish and Wildlife Service Pacific Southwest region said. "If he stays in California, that most likely won't be fruitful for him."