Omaha, the seat of Douglas County, is situated on the west bank of the Missouri River, 15 miles from its confluence with the Platte and 425 miles west of Chicago. It is the largest city in Nebraska and is sometimes called the "Crossroads of the Nation." The plateau on which Omaha is located, which extends along the west bank of the Missouri, had long been a meeting place before the arrival of whites. In 1804, Merriwether Lewis and William Clark met with Indians while on their westward journey to the Pacific. Jean Pierre Cabane established a trading post for the American Fur Company in 1825. The site of the post is now within Omaha's Hummel Park. The first settlers in the area were Mormons on their way west to Utah in 1846. Over the winter of 1846-1847, some 600 of their number died as a result of the terrible weather. The Winter Quarters Monument was erected on the site of their winter quarters in tribute to their suffering. In the early 1850s, people began to gather on the eastern side of the Missouri, in anticipation of a final treaty with the Omaha Indians, which would open Nebraska to settlement. On March 16, 1854, the Omahas ceded the land that now constitutes Douglas County to the United States, and the boom began. Although the Territory of Nebraska did not initially have a designated capital, the legislature held its first meetings in Omaha in 1855. Omaha remained the capital until 1867, when it was moved to Lincoln. A flood on the Missouri in 1877 caused the Missouri to change its course and strand about three square miles of Iowa on the Nebraska side of the river. The community, surrounded by Omaha, is known as Carter Lake. The Union Pacific Railroad established its eastern terminus in Omaha. A bridge across the Missouri to Council Bluffs, Iowa, was built in 1872, three years after the final spike had been driven at Promontory, Utah, linking the Union Pacific and the Central Pacific. The headquarters of Union Pacific are still in Omaha, but the Union Pacific Railroad Museum has been moved across the river to Council Bluffs. Omaha grew rapidly in the 1870s, with the creation of the Union Pacific shops and the establishment of Creighton University in 1878. St. Joseph's Hospital accepted its first patients in 1870. Further growth came in the following decade with the building of the Union Stockyards. Omaha hosted the Trans-Mississippi Exposition in 1898. Riverview Park was established by the city in 1894 and by 1898 had a number of animals donated by William Cody. The collection has developed into the Henry Doorly Zoo. The Douglas County Courthouse was erected in 1912, of Indiana limestone. The University of Omaha was founded in 1908 as a private, religiously oriented university. It became the Municipal University of Omaha in 1931 and began to receive city tax support. In 1968, it was integrated into the University of Nebraska. The College of St. Mary opened in 1923 and is now Nebraska's only all-women's Catholic college. Fort Crook was established south of Omaha in 1888. During World War II, the Martin Aircraft Corporation produced B-26 and B-29 bombers there, including the Enola Gay, the B-29 that dropped the first atomic bomb on Hiroshima on August 6, 1945. The fort has been incorporated into Offutt Air Force Base, the home of the Air Force's Strategic Air Command. Nebraska Methodist College is affiliated with the Methodist Health Systems and provides education for health professions. Nebraska Methodist Hospital is Nebraska's first Magnet Hospital. The Joslyn Art Museum has an eclectic collection starting from Greek pottery and extending into the 20th century. Local Omaha history is on display at the Durham Western Heritage Museum. The Omaha Children's Museum began operations in 1976 out of the back of a station wagon.