A common mode of indoor transportation is elevators, and ever since the 1800s, elevators have transported people and cargo up and down many buildings. Until the late 1800s, elevators were hardly even necessary, since buildings were never more than four or five stories tall. During the Industrial Revolution, however, steel beams and other new construction method allowed buildings to reach literal new heights, and indoor transportation had to keep up. Walking up stairs to the 20th floor would be tiresome, so residential lifts began to appear, and a commercial elevator or cargo elevator may be found in a factory or…