6. In 1870, 25 cities had 50,000 or more people. By 1890 cities had 50,000 or more people.
7. In 1870, 25 cities had 50,000 or more people. By 1890 58 cities had 50,000 or more people.
8. Louis Sullivan and other architects were able to build skyscrapers to meet the need for more space because of two factors: a. b.
9. Louis Sullivan and other architects were able to build skyscrapers to meet the need for more space because of two factors: a. the invention of elevators b. the development of internal steel skeletons.