"A Century of Progress International Exposition" was the name of a World's Fair held in Chicago, Illinois from 27 May 1933 (breaking for the winter months) to 31 Oct 1934 to celebrate the city's centennial. The theme of the fair was Technological Innovation. Its motto was "Science Finds, Industry Applies, Man Conforms." The fair was opened when the lights were automatically activated, when light from the rays of the star Arcturus was detected. The star was chosen as its light had started its journey at about the time of the previous Chicago world's fair, "The World's Columbian Exposition," in 1893. The rays were focused on photo-electric cells in a series of astronomical observatories and then transformed into electrical energy, which was transmitted to Chicago. The fair was wildly successful. For the first time in American history, an international fair had completely paid for itself, attracting in its two years, just short of 50,000,000 visitors.