The first European settlement on the present site of Chicago was the Mission of the Guardian Angel. Established in 1696 by Father Francois Pinet, a Jesuit priest, it was abandoned in 1700. In 1779, Jean Baptiste Point du Sable, a Haitian, built the first permanent settlement at the mouth of the Chicago River. Under the terms of the Treaty of Greenville in 1795, the Potawatomi Indians ceded a tract of land, six miles square, at the mouth of the Chicago River. The United States government began construction of a fort on that site in 1803. When it was completed in 1804, it was named Fort Dearborn after the secretary of war. Due to threats from both the British and Indians, the fort was abandoned soon after the outbreak of the War of 1812. Destroyed by the Potawatomi, the fort was rebuilt in 1816 and remained a military establishment until 1837. After Illinois was admitted to the Union in 1818, Chicago was designated in a series of counties, but ultimately settled in Cook County in 1831. Congress granted Illinois a right of way from Lake Michigan to LaSalle to build a canal. In 1829, the state legislature approved the construction of a canal that would connect Lake Michigan to the Mississippi River, using the Des Plaines and Illinois rivers. The first plat of the town of Chicago was filed in 1830. Incorporation as a town followed three years later. The origin of the name is unclear, but is generally believed to be derived from an Indian word meaning "strong." The original size of the town was only three eighths of a square mile, and its population was approximately 350. The area of the town was expanded in two steps to 2.4 square miles in 1835 with a population of more than 3,000. On March 4, 1837, Chicago became a city with a population of 4,170. The first civic election was held on May 2, 1837, and resulted in William Ogden becoming mayor. The year 1848 marked two momentous events in the history of Chicago. The first locomotive to reach Chicago arrived on a railroad designed to connect Chicago with the lead minds at Galena, Illinois. Also in 1848, the Illinois and Michigan Canal was completed. Within the next six years, the population of Chicago tripled. Since the first buildings in Chicago were built directly on the swampy ground, it was impossible to construct cellars or sewers. A Drainage Commission was organized in 1852 that adopted regulations in 1855 and 1856, specifying that the city achieve a new grade several feet above the level of the river. Streets were raised by covering them with dredgings from the river, as well as any other available material. Buildings were jacked up and foundations placed beneath them. By 1858, Chicago had risen a few feet above the mud. The first of many national political conventions to be held in Chicago was the 1860 Republican National Convention. Abraham Lincoln was nominated for the presidency on the third ballot. The fledgling Confederacy attacked Fort Sumter on April 12, 1861, and three days later, President Lincoln issued a call for volunteers. Chicago responded immediately with several companies of soldiers, such as the Chicago Light Artillery. Camp Douglas was opened on what was then open prairie, between 31st and 33rd west of Cottage Grove Avenue. On the night of Sunday, October 8, 1871, a fire started, allegedly in the cow barn behind Patrick O'Leary's cottage at 137 DeKoven Street. By midnight, the flames had jumped the river and by 2 a.m., the business district was ablaze. It then spread northward. By the time the flames had died out, 200 residents had died and $200 million damage had been inflicted. Chicago quickly recovered, however, and within four years had been largely rebuilt. In 1886, labor organizers strove for an eight-hour day and other improvements in working conditions. A confrontation at the McCormick Harvester plant on May 3 led to the death of one of the labor protesters. On the following day, when the police attempted to disperse a crowd protesting the previous day's incident, a bomb exploded, killing one policeman instantly. Seven more died later of their injuries. Eight men were brought to trial, and despite little evidence that they were connected with the bombing, they were convicted. Seven were given death sentences and another a long prison sentence. Four were hanged, one committed suicide, and two others had their sentences reduced to life imprisonment. In 1893, the governor of Illinois pardoned the three who remained in prison. Two World's Fairs have been held in Chicago. The 1893 Columbian Exposition commemorated the 400th anniversary of the discovery of America by Christopher Columbus. Jackson Park was converted into a White City of buildings, statues, and fountains. Afterwards, the Palace of Fine Arts was converted to the present Museum of Science and Industry. More than 27.5 million people attended. In 1933, the Century of Progress Exposition displayed human progress during the century of Chicago's existence. It was attended by 39 million visitors and was the first international fair in American history to pay for itself. Meigs Field was constructed on the site in 1946 and stayed in operation until 2003. The 1968 Democratic National Convention was held in Chicago during a period of increasing antiwar sentiment. Large numbers of Vietnam War protestors converged on the city and Mayor Richard J. Daley instructed his police to prevent any disruption of the convention. The heavy-handed response by the police was later characterized as a "police riot." Charges of incitement to riot were brought against seven radicals. Judge Julius Hoffman presided over their trial with a barely disguised pro-prosecution attitude. He sentenced the defendants and their lawyers to long terms for contempt of court, only to have the decisions overturned on appeal. He then handed down long sentences after convictions were returned on some of the counts, and again they were overturned, on the basis of judicial prejudice and FBI misconduct.