This article from HowStuffWorks explains how elevator systems work:
In the 1800s, new iron and steel production processes revolutionized the world of construction. With sturdy metal beams as their building blocks, architects and engineers could erect monumental skyscrapers hundreds of feet in the air.
But these towers would have been basically unusable if it weren’t for another technological innovation that came along around the same time. Modern elevators are the crucial element that makes it practical to live and work dozens of stories above ground. High-rise cities like New York absolutely depend on elevators. Even in smaller multi-story buildings, elevators are essential for making offices and apartments accessible to handicapped people. — Read More