World's Columbian Exposition, held at Chicago, May–Nov., 1893, in commemoration of the 400th anniversary of the discovery of America by Christopher Columbus. Authorized (1890) by Congress, it was planned and completed by a commission headed by Thomas W. Palmer (1830–1913), and the grounds along the Lake Michigan shore were dedicated Oct. 12, 1892. The exposition, known as the White City, comprised 150 buildings of Romanesque, Greek, and Renaissance architecture constructed of staff, a material resembling marble. Among the architects were Charles F. McKim, William R. Mead, and Stanford White, who designed the Agricultural Building; Richard M. Hunt, who designed the Administration Building; and Dankmar Adler and Louis H. Sullivan, who initiated functional architecture with the Transportation Building. Daniel H. Burnham supervised the design and construction; Frederick Law Olmsted, the landscaping. Popularly called the Chicago Fair, the exposition covered 600 acres (243 hectares), attracted exhibitors from 72 countries, and drew over 27 million visitors. It produced an unparalleled surge of creative energy that had an important influence not only in architecture but also on the cultural values of the nation.