The main idea is how sad it was to leave the farm.
Explanation:
The narrator goes on to tell us that people were crying, how much it was a horrible experience, and that there was many arguments. Although it talks about other things towards the end, the central idea is how sad it was to leave the farm.
He taught himself math, and was a maker of almanacs, an astronomer, and an author. Need to know more? Go here : http://www.biography.com/people/benjamin-banneker-9198038
