The gray wolf ( Canis lupus) in the 48 contiguous states has been on the Endangered Species List since 1967, with the only remaining mainland population at that time residing in Minnesota. (A population averaging about 25 has also inhabited Isle Royale National Park, Michigan). Federal research on Minnesota wolves began in 1969 and continues to the present, primarily in the Superior National Forest. This work has resulted in hundreds of scientific articles and books providing new information about wolves and their prey, and has trained numerous biologists and technicians, that have helped foster wolf-recovery and research efforts in many other states, including wolf restoration to Yellowstone National Park. Currently wolf populations are established in the following other states: Wisconsin, Michigan, Wyoming, Montana, Idaho, Washington, Oregon, New Mexico, and Arizona, and the USWS considers the wolf recovered. (Formal delisting has been thwarted several times by court cases citing legal technicalities.) Biologists conducting the current USGS wolf research have collaborated with researchers in Yellowstone, Alaska, and northern Canada, and have advised on similar projects in Italy, Spain, Scandinavia, Croatia, and the former USSR.