The Merchant Marine Act of 1920 (also known as the Jones Act) prevents foreign-flagged ships from carrying cargo between two American ports (a practice known as cabotage). Because of the Jones Act, foreign ships inbound with goods from Central and South America, Western Europe, and Africa cannot stop in Puerto Rico, offload Puerto Rico-bound goods, load mainland-bound Puerto Rico-manufactured goods, and continue to U.S. ports. Instead, they must proceed directly to U.S. ports, where distributors break bulk and send Puerto Rico-bound manufactured goods to Puerto Rico across the ocean by U.S.-flagged ships.