In 1945, Lawrence was elected mayor of Pittsburgh by a narrow margin. At the time, Pittsburgh was considered one of the most polluted cities in America, with smog so thick that it was not unusual for streetlights to burn during the daytime. Its industries had worked overtime during the war, adding to the pollution of air and water. Lawrence developed a seven-point program for Pittsburgh during his first days in office, making him one of the first civic leaders to implement a dedicated urban renewal plan. Republicans still controlled much of city politics and business at the time, so Lawrence had to forge bipartisan alliances to accomplish his objectives. His most famous partnership was with Richard Mellon, chairman of one of the largest banks in America and a staunch Republican. Despite their political differences, Mellon and Lawrence were both interested in the revival of Pittsburgh and both were early environmentalists. This partnership drove what came to be called the Pittsburgh Renaissance (later Renaissance I).