Final answer:
In 1807, the U.S. Congress passed a law banning the importation of slaves from Africa to the United States, which went into effect on January 1, 1808.
Step-by-step explanation:
In 1807, the U.S. Congress passed a law called the Act Prohibiting Importation of Slaves, which banned the importation of slaves from Africa to the United States. This ban went into effect on January 1, 1808. Therefore, it is true that after this date, importing slaves from Africa became illegal in the United States.
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