An escalator is a mechanized moving stairway, common in places with a lot of foot traffic or where a conventional staircase would be very long and tiring to climb. Escalators can often be seen in shopping malls, museums, multi-story parking garages, and subway stations, for example. Escalators are often installed in pairs, with an up escalator and a down escalator adjacent to each other, while a single escalator may be changed to go up or down according to the direction of heavier traffic at different times of the day.
An escalator is similar to a conveyor belt, but differs in that it is on an incline and has a surface of stairs rather than a flat belt. Most escalators also include a handrail that moves in conjunction with the stairs. To move from one end of an escalator to the other, a person may simply stand on one step until one reaches the end, or one may climb or descend the escalator like conventional stairs. Many escalators in busy areas are wide enough to accommodate two columns of people, and those who wish to stand conventionally remain on one side of the escalator.
The great majority of escalators in the world are straight, but there are some spiral models. These are generally used for their aesthetic appeal, but they also have the benefit of saving space. Spiral escalators may be seen in Caesar's Palace in Las Vegas, Nevada, the Westfield San Francisco Center in San Francisco, California, and the Times Square mall in Causeway Bay, Hong Kong.
Massachusetts patent lawyer Nathan Ames obtained the first patent for an escalator in 1859, though a working model did not appear until 1896. This was when Jesse W. Reno, a Lehigh University graduate in engineering, installed his 1891 escalator design in Coney Island, New York. More escalators began appearing in public places over the next few years, and they became increasingly sophisticated in design and exponentially more numerous throughout the 20th century. Now they are ubiquitous, with an estimated 90 billion people riding on escalators each year in the United States alone.