The purpose was to transport mail
In the early 19th century the owners of sugar plantations faced a huge problem. This was witnessed by water shortage as well as lack of labor.
Actually the real answer is the second and first world war pouring money into the us economy for output. If that is not an option it would be the invention of the steam engine and the 1800's locomotive industry.
North Korea pushed South Korea all the way to Pusan.
The major causes of World War II were numerous. They include the impact of the Treaty of Versailles following WWI, the worldwide economic depression, failure of appeasement, the rise of militarism in Germany and Japan, and the failure of the League of Nations.
