Wolves look like dogs, but they sometimes kill other animals. Two million gray wolves once lived in the United States. In the 1900s, they began dying out. The wolves often killed farm animals. Leaders let farmers hunt wolves. By 1974, gray wolves were nearly gone. Some scientists started raising gray wolves. In the 1990s, they let some of the wolves go. The wolves did well. Now, they want to let more go. Yet farmers say that this should not be done. They say that the wolves will kill too many farm animals.