then constructed of wood. Also, the lack of attention to proper waste disposal practices, which was sometimes deliberate to favor certain industries, left an abundance of flammable pollutants in the Chicago River along which the fire spread from the south to the north. The fire led to the incorporation of stringent fire-safety codes, which included a strong preference for masonry construction. The Danish immigrant Jens Jensen arrived in 1886 and soon became a successful and celebrated landscape designer. Jensen's work was characterized by a democratic approach to landscaping, which was informed by his interest in social justice and conservation, and a rejection of antidemocratic formalism. Among Jensen's creations were four Chicago city parks, most famously Columbus Park. His work also included garden design for some of the region's most influential millionaires. The World's Columbian Exposition of 1893 was constructed on former wetlands at the present location of Jackson Park along Lake Michigan in Chicago's Hyde Park neighborhood. The land was reclaimed according to a design by the landscape architect Frederick Law Olmsted. The temporary pavilions, which followed a classical theme, were designed by a committee of the city's architects under the direction of Daniel Burnham. It was called the "White City" for the appearance of its buildings. The Exposition drew 27.5 million visitors; is considered among the most influential world's fairs in history; and affected art, architecture, and design throughout the nation. The classical architectural style contributed to a revival of Beaux Arts architecture that borrowed from historical styles, but Chicago was also developing the original skyscraper and organic forms based in new technologies. The fair featured the first and until recently the largest Ferris wheel ever built. The soft, swampy ground near the lake proved unstable ground for tall masonry buildings. That was an early constraint, but builders developed the innovative use of steel framing for support and invented the skyscraper in Chicago, which became a leader in modern architecture and set the model nationwide for achieving vertical city densities. Developers and citizens began immediate reconstruction on the existing Jeffersonian grid. The building boom that followed saved the city's status as the transportation and trade hub of the Midwest. Massive reconstruction using the newest materials and methods catapulted Chicago into its status as a city on par with New York and became the birthplace of modern architecture in the United States. Rise of industry and commerce Chicago became the