Isle Royale National Park is a U.S. national park in the state of Michigan. Isle Royale, the largest island in Lake Superior, is over 50 miles (80 km) in length; it and multiple smaller islands along with all water to 2.5 miles of the outer islands make up the park. The island was once the site of a fishing industry, native copper mining and a resort community. Isle Royale National Park was established on April 3 1940.It was designated a Wilderness Area in 1976 and an International Biosphere Reserve in 1980. It is a small national park at 894 square miles (2315 km2), with only 209 mi2 (542 km2) above water. It is known for its wolf and moose populations which are studied by scientists investigating predator-prey relationships in a closed environment. There are usually around 25 wolves and 1000 moose on the island but the numbers change greatly year to year. In rare years with very hard winters, animals can travel over the frozen lake to the Canadian mainland. To protect the wolves from canine diseases, dogs are not allowed in the any part of the park including the adjacent waters. It is accessible by floatplane and by ferry during the summer months from Grand Portage, Minnesota and Houghton and Copper Harbor in Michigan. Private boats travel to the island mainly from Thunder Bay, Ontario, the closest city to the park. Some campgrounds are accessible only by private boat. It is the only major National Park Service park to close entirely in winter. Due to the difficulty of reaching the park and winter closing, only some 20,000 people a year visit Isle Royale. The park is not popular with day-trippers because, except for floatplanes and private boats, the only possible daytrips involve a three or four hour boat ride, only a two to three-hour lay-over before another three or four hour boat ride (if the weather is good). Boats may cancel trips during heavy weather. The Ranger III is a 165-foot (50 m) boat operated by the park. It is claimed to be the largest piece of equipment in the National Park system. It carries 125 passengers and canoes and kayaks and operates out of Houghton, Michigan, a six-hour trip from the park so it only travels one way each day. Currently it only goes to the park on two days a week, June to mid-September. The Isle Royale Queen out of Copper Harbor, Michigan and the Wenonah, out of Grand Portage, Minnesota operate round-trips daily in peak season. The Voyager, also out of Grand Portage, circles the island with an overnight at Rock Harbor, providing water taxi service from shore-side campgrounds. Isle Royale greenstone, (chlorastrolite, a form of Pumpellyite) is found here as well as on the Upper Peninsula of Michigan. It is the official Michigan state gemstone. The Greenstone Ridge is a high ridge in the center of the island and carries the longest trail in the park, the Greenstone Ridge trail, which runs 40 miles from one end of the island to the other. This is generally done as a 4 or 5 day hike. A boat shuttle carries hikers back to the start. In total there are 165 miles of hiking trails. There are also canoe routes, many involving portages along coastal bays and inland lakes. The park's two developed areas are Windigo, in the southwest with a campstore, showers and boat dock, and Rock Harbor in the northwest with campstore, showers, restaurant, lodge, campground and boat dock. There are 36 campgrounds spread across the island, some with three-sided shelters. Numerous small islands surround Isle Royale. Ships were once guided through the area by lighthouses at Passage Island, Rock Harbor, Rock of Ages, and Isle Royale Lighthouse on Menagerie Island.