Denver, established by a group of prospectors in 1858, is located at the confluence of the South Platte River and Cherry Creek. Near the foothills of the Front Range of the Rocky Mountains, Denver is also the county seat for Denver County, Colorado, and one of the few city/county governments that has been merged into one jurisdiction. Nicknamed "The Mile High City," Denver's official elevation, measured from the 15th step of the state capitol building's west side, is one statute mile (5,280 feet) above sea level. Founded in the Kansas Territory, the city's name was chosen to honor the territory's governor, James W. Denver. Prior to the U.S. Army's General Larimer placing cottonwood logs to stake out claims, the area had been used by the Cheyenne and Arapaho Indians for seasonal encampments. Larimer's intention was to create a major city that would cater to emigrants. Violating the 1851 Fort Laramie Treaty, he worked with agents at the Denver City Land Company to sell parcels in town to business owners and miners. Several months after the formation of the Colorado Territory, in November 1861, the city was incorporated. Until the Sand Creek Massacre of 1864, the Arapaho Indians continued to co-exist with the white settlers. After the brutal killing of 163 Arapaho, mostly women and children, at the hands of Colonel John M. Chivington, the remaining band were confined to reservations in Oklahoma and Wyoming. When the railroads arrived between 1870 and 1890, Denver grew from about 5,000 to more than 100,000 people. At that time, Denver became the second most populated city in the West, second only to San Francisco, California. Denver's first boom came to an end due to the depression of 1893, and the repeal of the Sherman Silver Purchase Act that was an attempt by President Benjamin Harrison to close the gap between the value of silver and gold. The growing disparity between the two metals resulted in the depletion of the U.S. gold reserves, an event that played prominently in creating the Panic of 1893. In an effort to diversify, governmental leaders promoted the raising of wheat and sugar beets, manufacturing, tourism, and service industries. The Denver Livestock Exchange and the National Western Stock Show anchored the city as the "cow town of the Rockies." Growth began to pick up slowly after 1900 as stockyards, brickyards, canneries, flour mills, leather, and rubber goods contributed to the city's improving economy. Of the many Denver-area breweries of this era, only Coors Brewing survived and has become the third- largest beer maker in America. Included in those efforts to diversify was the research and development of fuel sources in Colorado. Many oil and gas regional or national headquarters moved to Denver after World War II, fueling the growth of the city. Large skyscrapers of 40 and 50 stories began to spring up in the downtown area during the 1970s. Because of its proximity to a number of other distribution centers in the West and Midwest, the Mile High City became the nation's largest telecommunications center and one of the major national transportation hubs in the country. Denver also employed more federal workers than any other city, except Washington, D.C., as its population topped the 500,000 mark. The result of the energy crisis of the 1970s and early 1980s was a boon for Denver, as the city rapidly sprawled into surrounding areas with suburban subdivisions, malls, and a second office core in the suburban Denver Tech Center. America watched the energy boom on such television shows as "Dynasty." This boom came back to haunt Denver during the 1980s, when the price of oil dropped from $39 to $9 a barrel, in 1986. With that drop, Denver's economy went into a speedy and dreadful tailspin. As a result, Denver experienced a large exodus of people and the highest office vacancy rate (30 percent) in the country. Large layoffs included 15,000 people just in the oil industry, for example. However, other aspects in the energy and mining industries played an important role in the city's economic recovery. Under the leadership of Mayor Frederico Pena in 1989, construction began on the multi-million dollar Denver International Airport (DIA). After some unforeseen delays, the complex was completed in September 1994. At an original price tag of $60 million, failure of the airport's elaborate luggage dispersement system caused countless delays and cost millions of dollars to correct. When DIA finally replaced aging Stapleton International Airport, its construction cost totaled $5.2 billion dollars or nearly $2 billion over budget. The luggage system, which used acutators to move luggage from belt to belt, never worked effectively and was abandoned in 2005 by the last carrier to use it — United Airlines. In 2005, Denver became the first major city in America to make the private use of less than one ounce of marijuana legal for adults 21 and older. In a highly controversial and emotionally charged issue, Denver residents voted 53.5 percent to 46.5 percent in favor of its legalization. With the opening of the South Platte Valley for Coors Baseball Field, Elitch Gardens Amusement Park, Ocean Journey Aquarium, and Pepsi Athletic Center, there came a plethora of new housing projects. Denver is a prime example of urban sprawl with Boulder, Lakewood, Loveland, and Lafayette, all within close proximity of downtown. Each of these neighboring cities was originally established to provide housing for those wishing to escape the city, as well as find less expensive commercial and industrial space for businesses, but unchecked expansion has enveloped them, nonetheless. Historic Denver remembered Places of historic interest include the Colorado History Museum, which was built in 1977. The museum preserves a collection of historic and prehistoric artifacts and documents and is the Colorado Historical Society's headquarters. In addition to exhibits and educational programs, the museum includes the Stephen H. Hart Library, the Office of Archaeology and Historic Preservation, and a membership services division. Other highlights of the Mile High City are the Denver Art Museum and the Denver Center for the Performing Arts, as well as the Denver branch of the U.S. Mint, where tours are available. The Museum of Nature and Science opened in 2003, and includes the Gates Planetarium, which has one of the most technologically advanced, immersive digital theaters of its kind in the world. Denver sports Denver plays home to major league baseball, basketball, football, hockey, and soccer teams. Those teams include the Denver Broncos of the National Football League, Colorado Avalanche (NHL), Denver Nuggets (NBA), Colorado Rockies Major League Baseball team, and the Colorado Rapids Major League Soccer team. Other outdoor activities in town include the Denver Zoo city park with its rain forest habitat for jungle primates and other wild animals. Food vendors compliment scheduled tours of the zoo.