industrialization (1800s but not sure if it was late 1800s...):
-economic development- led to more factories & factory workers
-development of railroads (especially railroads that made it easier to move, transported materials & trade) new technologies and innovations like steamships, spinning jenny, cotton gin... etc...
-people in many parts of the world started moving to the US for better opportunities
this led to people from diff parts of the world to migrate to the US (better to write about for late 1800s):
-extreme hardship
-war
-lack of economic opportunities/high unemployment
then theres new places (such as the US) where your overhear about:
-more jobs
-promise of a better life
-freedom to practice ones religion
-an overall better standard of living