the automobile
conformity
The Cotton Gin
astrolabe
Refrigerated railroad cars.
The railroad.
Problems in the cities
Problems in the cities
Nikola Tesla
The microcope
Problems in the cities
The Steel Plow helped the people a lot.
the invention of the printing press
It was the invention and usage of a zero symbol
The one thing that helped to spurn the growth of the suburbs was the need for laborers to support factory operations, which were located in urban areas.
It helped them defend their cities.
conformity
it helped it a lot