Some of the negative effects of the Age of Exploration were the huge death tolls suffered by Native American populations as a result of wars and transplanted European diseases, the destruction of pre-existing New World civilizations and the establishment of the Atlantic Slave Trade. Although the intent was to find a new route to Asian trade markets by sailing west from Europe, the discovery of the previously unknown American continent in 1492 also created a new market for the gold and silver found there. The Spanish conquistadors soon began a successful and often devastating campaign of conquest against indigenous civilizations , as they moved across the southern portion of the continent in search of the highly prized precious metals.
An estimated 70 to 90 percent of the Native American population was lost due to European diseases. The Europeans' systematic extraction of wealth and resources from native lands, particularity through the Spanish conquistadors' use of warfare and forced labor, also added to the death toll.
The cash crops of sugar, tobacco and cotton that sprang up in the Americas required extensive amounts of hard labor and gave rise to the Atlantic Slave Trade. During the almost 400 years of the slave trade, between 11 and 15 million slaves were transported to the New World from Africa in what became the largest forced sea-borne migration in history. Estimates point to a third of the enslaved voyagers not surviving the journey across the Atlantic Ocean. The United States placed a ban on the importing of African slaves in 1808, but the practice of slavery remained legal until the 13th Amendment was passed in 1865.