emissions from coal burning close to the ground, resulting in "the day the sun didn't shine". A cloud of thick black smoke enveloped St. Louis, far worse than any previously seen in the city. The day came to be known as "Black Tuesday". The smog hung about for nine days over the course of the following month. This proved to be the catalyst that forced the council's hand. New cleaner, affordable supplies of coal (semi-anthracite) were quickly secured from Arkansas in time for the next winter. This, together with a new smoke ordinance, improvements to the efficiency of furnaces and the ongoing public education campaign resulted in a significant and permanent improvement in air quality in the city. See also Donora Smog of 1948 1966 New York City smog Jewel Box (St. Louis, Missouri), a municipal greenhouse that was built because of high smog and soot levels 2013 Eastern China smog 1930 Meuse Valley fog Great Smog of London Pea soup fog References Further reading Tucker, Raymond R. Smoke prevention in St. Louis (Ind. Eng. Chem., 1941, 33 (7), pp 836–839) Earthways Center. In the Air: In a shroud of smoke, Student Booklet 3-6. External links History of Pollution problems. Anti-Smoke Campaign. Smog events 1939 St Louis Smog, 1939 Air pollution in the United States 1939 in the environment saint louis