@earthsignalofficial: In the 1940s, Pittsburgh's steel mills and coal furnaces filled the valley with so much smoke that city authorities sometimes switched on the streetlights at midday. A smoke control ordinance was passed in 1941, delayed by World War II, and finally enforced in 1946 under Mayor David Lawrence, who vowed to clean up the city. Over the following decades, the mills closed or cleaned up, soot was sandblasted off the downtown skyscrapers, and new laws cut pollution in the air and water. Today the skyline stands clear against the hills. The story isn't finished, since the Pittsburgh region still ranks among the worst U.S. metro areas for fine particle pollution, but the contrast with the 1940s is one of America's clearest proofs that polluted air can be cleaned up. #EarthSignal #Pittsburgh #ThenAndNow #UrbanTransformation #PatternsHidingInPlainSight 📍 Pittsburgh, Pennsylvania, USA

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Tuesday 03 November 2026 23:00:54 GMT