African slaves were originally chosen because where the Europeans landed on Native land, the Native Americans were dying off from diseases and sickness. Many African leaders had a hand in this for money purposes: weapons, tobacco, and gold.
States were also given a chance to propose changes, or amendments. Three-fourths of the states have to approve the amendment for it to become law. In the past 200 years, the Constitution has been amended 27 times. The 13th Amendment, in 1865, forever banned the practice of slavery.