What was the greatest contribution made by Elisha Otis to the development of the "modern" elevator?

The greatest contribution made by Elisha Otis to the development of the modern elevator was the creation of the safety-equipped elevator. In the mid-19th century, Otis developed a safety system that prevented elevators from falling if the hoisting cable broke. This innovation significantly increased the safety of elevator systems and allowed for the widespread adoption of elevators in multi-story buildings, as it addressed concerns about passenger safety. Otis demonstrated his safety device at the 1854 World's Fair, which garnered public attention and confidence in using elevators, facilitating the growth of skyscrapers and modern urban architecture.

While other innovations in elevator technology, such as hydraulic systems, gearless traction mechanisms, and automatic doors, are important advancements, Otis's safety mechanism was pivotal in changing perceptions and enabling the expansion of vertical transportation. His work laid the foundation for the modern elevator industry, emphasizing the importance of safety as a critical component in its development.