Why did slavery expand in the nineteenth century instead of dying out, as some Americans had predicted after the Revolution?

Because During the first half of the nineteenth century, the demand for cotton led to the expansion of plantation slavery.

president jefferson protested this interference in american trade. he sent james monroe to london to negotiate a treaty. jefferson wanted britain to stop taking sailors from american ships, and to stop interfering in the trade of neutral nations. monroe tried many times to discuss such an agreement. but the british foreign minister was always too busy to see him.

explanation:

c.) the country needed a stronger central government.