Why did the spanish and portuguese begin using african slaves in their new world colonies in the 1500s?

What were four reasons for the decline of spain as a world power

Plz ! the election marked the last time the federalist party ran a candidate for president. a. 1812. b. 1820. c. 1816. d. 1824.

In what is known as the great migration, large numbers of african americans moved from the rural south to northern cities, beginning in the early twentieth century. what motivated this large-scale movement?