It's hard to believe Chicago started out as a small trading post at the mouth of the Chicago River. It incorporated as a city on March 4, 1837, and grew exponentially in the decades that followed. Most of its buildings were made of wood. During the dry summer of 1871, a massive fire broke out, destroying more than 17,000 buildings across Chicago and killing 300 people. The cause of the fire was never determined. This photo shows the fire's devastation at the corner of State Street and Madison Street.



Editor's note: An earlier version of this gallery had an image of downtown Chicago that was removed because its authenticity was in question. After further review with the source, CNN found the image was misrepresented as an historical photograph. It was in fact a still from the 1937 movie "In Old Chicago." CNN regrets the error. Chicago History Museum/Getty Images

It didn't take long for Chicago to rebuild after the devastating fire of 1871. To celebrate its return, Chicago hosted the World's Fair in 1893. Several buildings were designed for the event, including the Agricultural Building, seen here. That year's fair was known as "The White City," and it is the backdrop for Erik Larson's nonfiction novel "The Devil in the White City." The book is reportedly being made into a film starring Leonardo DiCaprio. Museum of Science and Industry, Chicago/Getty Images

A soda parlor is seen on Chicago's South Western Avenue in 1895. The Chicago Tribune newspaper, shown here being sold for 1 cent, is still in publication today. AP

Chicago's famous "L" (short for "elevated" train) started moving residents around town in 1892. That makes it the second-oldest transit system in the country behind the one in Boston. Here, a steam-powered "L" train comes down the railway on Market Street near Lake Street on June 30, 1895. Hulton Archive/Getty Images

One of the worst tragedies to strike Chicago happened on July 24, 1915, when the SS Eastland capsized in the Chicago River with 2,500 passengers aboard. The passenger ship was docked at the time. The cause of the disaster is still unclear. Some have speculated that the Eastland had a faulty ballast system or additional lifeboats that made it top-heavy. More than 840 people died after passengers spilled into the river, while others -- mostly women and children -- were trapped in underwater cabins. Here, survivors stand atop the capsized vessel. AP

Chicago's National League baseball team started out as the White Stockings in 1876 before a newspaper's nickname prevailed and the team adopted the "Cubs" nickname. A shortened version of their old name went to the American League team in Chicago, and the two teams played each other in an all-Chicago World Series in 1906. The White Sox won. AP

This 1921 photo shows baseball commissioner Judge Kenesaw Mountain Landis, rear left, during the investigation of the infamous "Black Sox" scandal in Chicago. Eight White Sox players received life suspensions from baseball after being accused of accepting bribes to lose the 1919 World Series. AP

The Chicago Bears football team plays during the 1920s. The Bears, one of the founding franchises of the National Football League, started out as the Decatur Staleys in 1919. AP

Cars prepare to race at Soldier Field. The stadium, on Chicago's South Side, first opened in 1924 and is still the home of the Chicago Bears today. ISC Images and Archives/Getty Images

An aerial view of Chicago, circa 1930. The large white building on the Chicago River is the Merchandise Mart, with 4 million square feet of floor space spanning two city blocks and rising 25 stories. It was the largest commercial building in the world when it opened in 1930. Underwood Archives/Getty Images

Police and spectators gather in front of the garage on Chicago's North Clark Street, where members of Al Capone's gang, disguised as policemen, shot and killed seven members of a rival gang on February 14, 1929. The St. Valentine's Day Massacre became a symbol of the extreme violence of the Chicago underworld and crime boss Al Capone. Chicago History Museum/Getty Images

Al Capone -- on the left, wearing the all-white hat -- leaves a Chicago courtroom in the custody of U.S. marshals in October 1931. Capone ran gambling, prostitution and bootlegging operations across Chicago until he was indicted in 1931 for tax evasion. He was convicted and spent the next 11 years in prison. AP

Bartenders at Sloppy Joe's bar in downtown Chicago pour a round of drinks in 1933 to celebrate the repeal of the 18th Amendment and the end of the Prohibition era. American Stock/Getty Images

Famous bank robber John Dillinger met his demise at Chicago's Biograph Theater, where he attended a performance with Anna Sage, a friend and brothel madam and -- unbeknownst to Dillinger -- an FBI informant. Dillinger was shot and killed after he emerged from the theater on July 22, 1934. This aerial view shows Dillinger's body being taken from a funeral home in Chicago two days after his death. AP

Armed with guns, clubs and tear gas, Chicago police put down a crowd of striking workers outside Chicago's Republic Steel plant on May 30, 1937. They killed 10 unarmed demonstrators and injured dozens in what was later called the Memorial Day Massacre. News cameras captured the brutality. Carl Linde/AP

A Chicago subway station is seen on July 18, 1944. Hedrich Blessing Collection/Chicago History Museum/Getty Images

Queen Elizabeth II enters the Grand Ballroom of the Hilton Hotel in Chicago on July 6, 1959. She was attending a banquet held by Chicago Mayor Richard J. Daley, seen at left in the bow tie. Daley and his son, Richard M. Daley, presided over Chicago as mayor for 42 combined years. Edward Kitch/AP

Chicago police drag away one of 80 civil-rights marchers who were arrested after staging a rush hour sit-in on a downtown street in Chicago on June 28, 1965. Leaders of the march, dissatisfied with results of a two-hour meeting with the mayor, ordered marchers to assume "arrest position." Eric Marrapodi/CNN

Members of the New York delegation protest the Vietnam War at the 1968 Democratic National Convention, which was held in Chicago. Chicago is a popular city for national political conventions, having hosted more than two dozen in its history. But the city was not quite prepared for the mayhem in 1968, despite a contingent of federal troops to help keep the peace. Getty Images

United Airlines Flight 553 plowed through a row of bungalows and burst into flames about a mile and a half south of Chicago's Midway Airport on December 8, 1972. The crash killed 45 people, two of them on the ground. Eighteen passengers survived. Investigators later ruled that pilot error caused the crash. AP

Chicago Bears head coach Mike Ditka is carried off the field by his players after the team won Super Bowl XX in January 1986. It is the Bears' only Super Bowl victory. Phil Sandlin/AP

Anyone who watched Michael Jordan play for the Chicago Bulls in the 1980s and 1990s knows why he's widely considered to be the greatest basketball player of all time. Jordan led the Bulls to six NBA titles in an eight-year span. Focus on Sport/Getty Images

Against the backdrop of Chicago's Sears Tower, sailboats are set for the start of the Chicago Yacht Club Race to Mackinac in July 2003. It is the world's longest annual freshwater race, having started in 1898. Jeff Haynes/AFP/Getty Images

One of Chicago's most famous residents, Oprah Winfrey, sits atop a brand new car -- one of hundreds that she gave away to audience members in 2004 -- outside her Chicago studios. Winfrey moved her talk show to Chicago's West Loop in 1988, purchasing an 88,000-square-foot facility in the neighborhood, which was struggling at the time. She is now reportedly considering selling Harpo Studios, which helped revitalize the neighborhood. Bob Davis/Harpo Productions/AP

The Chicago White Sox celebrate after winning the 2005 World Series with a four-game sweep over the Houston Astros. It was the team's third World Series title and first since 1917. G. N. Lowrance/Getty Images

Every year since 1961, the downtown section of the Chicago River has been dyed green to celebrate St. Patrick's Day. Scott Olson/Gett Images

Barack Obama and his family celebrate in Chicago's Grant Park after he won the presidential election on November 4, 2008. Obama first moved to Chicago after college to work as a community organizer. He went on to finish Harvard Law School and returned to Chicago to teach constitutional law at the University of Chicago. He worked as a civil rights attorney and a state senator before being elected to the U.S. Senate in 2004. First lady Michelle Obama was born and raised on Chicago's South Side. Emmanuel Dunand/AFPGetty Images