Who invented the skyscraper?
William LeBaron Jenney, for the Home Insurance Building in Chicago. He took the weight off the walls and put it on a metal frame. Almost every part of that sentence has been argued over since.
The short answer
William LeBaron Jenney (1832 to 1907) trained as an engineer and ran an architecture office in Chicago after the fire of 1871. His Home Insurance Building went up at LaSalle and Adams between May 1884 and 1885. It had ten stories at first and 12 after an extension in 1891, which brought it to 55 m (180 ft). It was demolished in 1931 to clear the site for the Field Building.
The building was not tall by any later standard, and masonry offices in Chicago already reached a similar height. What was new is where the load went: the floors and the brick skin rested on a grid of cast-iron columns and wrought-iron and steel beams, so the outer wall carried only itself. The building weighed about a third of what the same volume of masonry would have, and the walls could be thin enough to hold large windows. That is why the United States, and Chicago in particular, gets named as the place where the skyscraper was invented.
The Chicago Skeleton
The frame Jenney used became known as the Chicago Skeleton. A thick masonry wall has to get thicker with every story added, until the ground floor is mostly wall and the windows are slits. A metal cage does not, and the wall above the first floor becomes a curtain hung on the structure.
Local conditions pushed Chicago into it. The fire of 1871 had burned out the business district, so fireproofing was a hard requirement and iron columns were cased in brick and terracotta. Downtown Chicago also sits on soft clay, where a lighter building meant a cheaper foundation. Bessemer steel had fallen in price through the 1870s, which made the frame affordable at the moment the city needed one.
Why the credit is disputed
The Home Insurance Building was gone by 1931, and the case for it rests on records and on an investigation the Marshall Field estate commissioned while it was being taken apart. Iron framing was also older: the Ditherington Flax Mill in Shrewsbury, England, stood on one in 1797. Philadelphia's Jayne Building of 1850 and New York's Equitable Life Building of 1870 get called proto-skyscrapers, and the Equitable had passenger elevators. In Chicago the Montauk Block of 1882, by Burnham and Root, is sometimes given the title.
Then there is Leroy Buffington of Minneapolis, who patented a 28-story iron-framed "cloudscraper" in 1888 and spent the 1890s suing other architects for infringement. He lost, but the lawsuits show how contested the question was while the people involved were alive. Historians have since argued that Jenney's title owes a good deal to how well Chicago architects promoted it after the fact.
The usual resolution is to narrow the claim: Jenney's building is the first tall commercial building whose exterior masonry was carried entirely by the metal frame, and that is the detail every later tower copied.
Jenney the engineer, Sullivan the artist
Ask who invented the modern skyscraper and the answer is often Louis Sullivan. Sullivan worked in Jenney's office as a young draftsman before setting up with Dankmar Adler, and his Wainwright Building in St. Louis of 1891 did something Jenney had not attempted. He stopped dressing the frame as a stack of classical floors and gave the building continuous vertical piers from base to cornice, so the height became the subject of the design. He also wrote the sentence the whole argument runs on, in 1896: form follows function.
Sullivan is called the father of the skyscraper for the look, Jenney the father of the skyscraper for the structure. The two claims answer different questions, and the history page sets out how the day itself ended up tied to Sullivan's birthday on 3 September.
Elisha Otis and the part that made it usable
A ten-story office with stairs only has nine floors nobody wants, and the problem with a hoist was the rope: if it broke, the platform fell. Elisha Graves Otis built a spring-loaded brake that gripped the guide rails when rope tension went slack, and demonstrated it at the New York Crystal Palace exhibition in 1853 by having the rope cut above him while he stood on the platform. The first passenger installation followed in 1857, in the E. V. Haughwout store on Broadway. Nobody calls Otis the inventor of the skyscraper, but without the brake the frame would have produced tall warehouses. With it, the top floor became the expensive one.
When the word "skyscraper" meant a building
The word is older than the thing. It named anything that stuck up absurdly far: a high-standing horse in 1788, a light triangular sail above the skysail on a square-rigger in 1794, a tall hat around 1800, a very tall man in 1857, a rider on a high-wheeled bicycle in 1892.
The use for a tall building is recorded from 1888, in Chicago, three years after the Home Insurance Building opened, so the first skyscraper was not called one while it was going up. Nobody coined the word for architecture: newspaper writers reached for existing slang for something outlandishly tall and it stuck to the new offices.
What counts as a skyscraper is a question of definition more than of height. The tallest building in the world is settled by a measuring body and a rulebook, and the same is true of the first one.