during its first century as a city, chicago grew at a rate that ranked among the fastest growing in the world. within the span of forty years, the city's population grew from slightly under 30,000 to over 1 million by 1890. by the close of the 19th century, chicago was the fifth largest city in the world. within fifty years of the great chicago fire of 1871, the population had tripled to over 3 million.