The City of Chicago's database of buildings as of December 2014 includes more than 378,000 homes, office buildings and businesses. Data showing when those buildings were built exists for more than 206,000 of them, with the earliest year being 1853 and latest 2007. Sorting those records by decade shows the biggest boom in building Chicago taking place in the 1920s with nearly 40,000 new buildings being built. The South Loop church where a piece of a decorative gargoyle fell and killed 34-year-old Sarah Bean was finished in 1874, a decade that saw at least 2,429 buildings built according to the city data. The great fire burned in 1871, so it would seem natural that the 188s saw a building boom of some 12,000 structures.
Source: City of Chicago data portal