What was the Monroe Doctrine and what impact did it have on American history

Answer only ONE of the below questions:
What was the Monroe Doctrine and what impact did it have on American history? Is it still relevant today?
or
Discuss any ONE discovery or improvement in the areas of transportation or industry (steam engines, steam ships, roads, canals, railroads, cotton gin, McCormick Reaper, Colt revolvers, etc..) that had a signifigant impact the U.S. from around 1800-1850.
or
Who is your favorite American author from the period 1800-1850? Why?
or
Which of the following reform movements of the early 1800s do you beleive had the greatest impact on American history? a. the Abolition Movement b. the Women’s Rights Movement c. the Temperance Movement
Post your response of (minimum) 250 words in a neat, detailed, and thoughtful fashion. Then respond to at least two other student posts in a meaningful way (a minimum of 50 words each). You must post in YOUR OWN WORDS (no copying/pasting from the internet, etc.).