The president who was famous for not being able to tell a lie was Abraham Lincoln. The first president was George Washington.
The main reason why the United States was so interested in the security of Latin America is because the Latin American countries were so close to the US, meaning that if they were invaded by European powers it would post a threat to the US.
Sampling, mark and recapture, indirect observation, and direct observation
Many nations had already abolished slavery.
Let me know if you want to know why.