This is true.
Only about 450,000 African slaves ended up in the United States until the U.S. Congress abolished the African slave trade in 1807. About 500,000 altogether ended up in various parts of North America, outside of the Caribbean islands.
The West Indies and Brazil imported the largest percentages of slaves. Brazil received 4.86 million Africans. This is why, today, Brazil has the largest population of people of African descent outside of Nigeria.
The Caribbean was the second main consumer of slaves. They imported approximately 4.5. million. On the Caribbean islands, particularly the Barbados and Cuba, the sugar trade was very important. Slaves were needed to cut sugar cane. However, conditions on these islands, due to the heat and the prevalence of disease, caused many slaves to die. When this occurred, more slaves had to be brought in to replenish those who had died.
In the American Colonies, most slaves were taken to two states: Virginia and South Carolina. Virginia had a successful tobacco trade. Slaves were needed to cultivate and pick the tobacco plants. In South Carolina, the cultivation of rice became lucrative. In 1803, after the Louisiana Purchase, the United States became more interested in the cultivation of cotton. Textile mills in New England, particularly, and Great Britain depended on Southern cotton. Alabama, Mississippi, and eastern Texas were pre-eminent in the cultivation and sale of cotton. The speed of cotton cultivation improved with the invention of Eli Whitney's cotton gin in 1794.
Because of the cultivation of cotton, and the remaining importance of the other crops, slaves were still highly desirable property -- up until the outbreak of the Civil War in 1861. To acquire the slaves that were necessary, it was not unusual for free Northern blacks to be kidnapped and brought South.