This material lasts longer than iron, but was more expensive in the 1870s:
What is steel
100
This was the average weekly salary for children in factories:
What is 1-3 dollars a week
100
The name of the war that the rise of industry followed
What is The Civil War
200
This factory invention had interchangeable parts, and had one or two workers each doing the same task in order to make cars:
What is an assembly line
200
The number of millionaires from 1860 to 1892 was between these two numbers:
What is 400 and 4000
200
This dangerous occurrence destroyed factories and killed many:
What is fire
300
Although Thomas Edison had his first working practical light bulb in 1879, this later year is the time when his first electrical distribution system was set up in New York City:
What is 1882
300
This number is at least how many light bulbs were beings used in 1900:
What is 25 million
300
The name of this age, which represented the wealth of people at the time:
Bonus points: The name of the man who coined this phrase