The best marketplace in the United States will depend on what it is you're selling and who your target audience is. With that said, the most recognized marketplaces in this country are:
1. Amazon
2. eBay
3. Walmart
4. Etsy
All of these marketplaces have great reputations, offer great customer service, and are trusted by consumers. This makes them great prospects for those who are looking into opening an online shop in a marketplace.