Why and how did Cuba and Puerto Rico become prosperous sugar colonies in the mid-19th century?

90,000 slaves imported into Cuba from 1856-1860. As soon as Spain opened Cuba's ports up to foreign ships, a great sugar boom began that lasted until the 1880s.

Explanation:

After the U.S. and most European countries and slavery, Spain and Caribbean pick up the slack and continue slave trade through the 19th century, increasing slave imports through the 1860s. The island was perfect for growing sugar, being dominated by rolling plains, with rich soil and adequate rainfall.

Explanation:

the awenser wuold be slaves

honestly you should get that checked out because it really isn't normal