When complete, the Monadnock was the largest office building in the world, with 1,200 rooms and an occupancy of over 6,000. The "Chicago Daily Tribune" commented that the population of most Illinois towns in 1896 would fit comfortably in the building. It was a postal district unto itself, with four full-time carriers delivering mail six times a day, six days a week. It was the first building in Chicago wired for electricity, and one of the first to be fire-proofed, with hollow fire clay tiles lining the structure so that the metal frame would be protected even if the facing brick were to be destroyed.