"In the 1880s Chicago was experiencing explosive growth that propelled land values to levels no one could have imagined, especially within the downtown "Loop," named for the turn-around loops of streetcar lines. As land values rose, landowners sought ways of improving the return on their investments. The sky beckoned. The most fundamental obstacle to height was man's capacity to walk stairs, especially after the kinds of meals men ate in the nineteenth century, but this obstacle had been removed by the advent of the elevator"