Question

The two most important new technologies that enabled the development of the skyscraper were

Answer 1

These two technologies were the development of a  safe elevator  and the method of building using a grid of steel beams. 

In 1853, an American inventor called Elisha Graves Otis developed a safety device that kept elevators from falling should a  cable break. This new development had an enormous impact on public confidence. Later in the century, the change to an electric motor made the elevator a practical solution to the problem of getting up and down tall buildings.

In Chicago during the 1880s, lack of space for building became a problem due to a high rate of development, and the only alternative was to build upward. Construction techniques had to change and so a new method of building was developed that used a grid of steel beams and columns that were strong enough to support any stresses or forces a building may experience. With this new building method, the skyscraper was born.