In the United States, the terms yam and sweet potato are often used interchangeably, but they are completely different vegetables. In the United States, the terms yam and sweet potato are often used interchangeably, but they are completely different vegetables. Yams are dry, starchy, and have rough, brown skin. They can grow up to 45 feet long, and can be found in West Africa, the Caribbean, and Asia. Sweet potatoes are a New World root vegetable. They have a soft, creamier interior, a smoother skin, and many variations in color; from creamy white to deep, ruby orange.   If you live in North America, chances are good you've never eaten a real yam. True yams are almost impossible to find in North America! In fact, if you are an American, it’s very likely that you have never eaten a real yam! Real yams originated in and are now mostly commercially grown in Africa. The two top-producing sweet potato states in the nation are North Carolina and California.