The revolving door was invented because it has several advantages over conventional hinged doors.

And no, it was NOT created in order to keep horses out of buildings. In 1888, the revolving door was invented by Philadelphia native Theophilus van Kannel. This entrance would soon become the customary entrance to most modern skyscrapers for its superiority over many aspects of hinged doors. Revolving doors help to serve as an airlock, which keeps out cold air and helps to drive down heating costs. They also help to soundproof the lobby of a building by keeping out street noise and eliminating the slamming of doors.

These doors also reduce the possibility of a collision between people who are coming and going. Another benefit in skyscrapers and other large buildings is that the difference in air pressure caused by large amounts of heated air does not make opening a revolving door difficult as it often does with hinged varieties. Architects are also big fans of revolving doors because entering a confined space before you step into a building makes the building seem that much larger and more majestic. In 1889, Van Kannel was awarded the John Scott Medal by the city of Philadelphia for the usefulness of his invention to society.
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