What made it possible to construct skyscrapers in the 1800s

It was made possible by the new methods of making steel

Explanation:

The Bessemer process was the first inexpensive industrial process for the mass production of steel from molten pig iron prior to the development of the open hearth furnace. The key principle used was the removal of impurities from the iron by process of oxidation with air being blown through the molten iron. The oxidation also enhances the temperature of the iron mass and keeps it molten. So with the presence of this, building of skyscraper was made possible.