and Falconbridge in 1928. They became two of the city’s major employers and two of the world's leading producers of nickel.
Through the decades that followed, Sudbury's economy went through boom and bust cycles as world demand for nickel fluctuated. Demand was high during the First World War when Sudbury-mined nickel was used extensively in the manufacturing of artillery in Sheffield, England. It bottomed out when the war ended and then rose again in the mid-1920s as peacetime uses for nickel began to develop. The town was reincorporated as a city in 1930. The city recovered from the Great Depression much more quickly than almost any other city in North America due to increased demand for nickel in the 1930s. Sudbury was the fastest-growing city and one of the wealthiest cities in Canada for most of the decade. Many of the city's social problems in the Great Depression era were not caused by unemployment, but due to the difficulty in keeping up with all of its new infrastructure demands created by rapid growth. Between 1936 and 1941, the city was ordered into receivership by the Ontario Municipal Board. Another economic slowdown effected the city in 1937, but the city's fortunes rose again during the Second World War. The Frodo Mine alone accounted for 40 percent of all the nickel used in Allied artillery production during the war. After the end of the war, Sudbury was in a good position to supply nickel to the United States government when it decided to stockpile non-Soviet supplies during the Cold War.
Compounded by open coke beds in the early to mid 20th century and logging for fuel, the area suffered a near-total loss of native vegetation. Consequently, the region became blanketed with exposed rocky outcrops permanently stained charcoal black, first by the air pollution from the roasting yards then by the acid rain in a layer which penetrates up to three inches into the once pink-gray granite. The construction of the Inco Super stack in 1972
