This is of course a very complex question that does not have a definitive answer, but 1850s would be a good decade to start counting as "Modern". This was a decade of the telegraph and Darwin's The Origin of Species.
<span />
The size and growth rate of the human population has changed in the past 200 years because reproduction rates have increased due to the large number of people in the world
Answer:
Railroads
Explanation:
The western side of America is known to be as the region of Great Plains. The area with mountains and desert led the region to be famously known for Indians, cowboys, outlaws, prospectors, and covered wagons on trails. With no river system and roads to connect with the other side of America, railways became major transportation in supplying crops.
