Anchorage, a year-round seaport at the head of Cook Inlet, is the largest city in Alaska. Its location has made it an important transshipment point for intercontinental air traffic, and the lack of a comprehensive highway system led to its having an unusual concentration of private aircraft as well. Cook Inlet was discovered and named by Captain James Cook in 1778. Russian explorers had already been to Alaska and Russian activity continued until the Alaska Purchase of 1867. The Alaska Trading Company subsequently established dozens of stations along Cook Inlet. In 1915, President Woodrow Wilson authorized the construction of the Alaska Railroad. Anchorage was founded in the same year as the headquarters of the railroad and was incorporated in 1920. Completion of the Alaska Railroad led to the first visit to Alaska by a U.S. President. Warren G. Harding came to Alaska to drive the ceremonial golden spike on July 15, 1923. He died in San Francisco on the return trip. The city grew rapidly during World War II as the headquarters for the Alaska Defense Command of the U.S. Army. Elmendorf Field and Fort Richardson were built during the war. Between 1940 and 1951, the population of Anchorage rose from 3,000 in 1940 to 47,000 in 1951. In the 1950's, the highway linking Anchorage and Seward was completed, opening the Kenai Peninsula to motor vehicles. The Great Alaska Earthquake in 1964 devastated much of downtown Anchorage, but rebuilding was rapid. When oil was discovered at Prudhoe Bay on Alaska's North Slope, Anchorage was the logical place for oil companies to site their headquarters and Anchorage boomed again. By the end of the 1970's, the greater Anchorage area had half the entire population of Alaska. To create better government efficiency, the city of Anchorage merged with the surrounding borough to form the Municipality of Anchorage in 1975. The Anchorage Museum of History and Art displays the art and history of Alaska and the circumpolar north. The Imaginarium is a science discovery center for children and has operated since the 1980's. The Alaska Native Heritage Center provides a place to experience the many aspects of Native culture in Alaska. The Alaska Heritage Museum, located in the Wells Fargo Building, was established in 1968 by the National Bank of Alaska. Begun in 1959 as Alaska Methodist University, Alaska Pacific University is a private, liberal arts college. The University of Alaska Anchorage is the largest four-year university in the state. Providence Alaska Hospital is the state's largest and traces its history of caring to the arrival of the Sisters of Providence in Nome in 1902. In 1963, Alaska Presbyterian Hospital was founded. It later changed its name to Alaska Regional Hospital and has been associated since 1994 with the national HCA chain of hospitals.