The United States has two major securities markets, the New York Stock Exchange (NYSE) and the NASDAQ Stock Market (NASDAQ), using different trading structures to handle roughly equivalent daily trades of similar value.

The NYSE is the world's largest specialist-trading system, providing a traditional, floor-based auction for trading securities. Every NYSE firm is assigned to a single trading specialist firm which receives orders to buy and sell shares in that company from numerous broker dealers. The specialist ensures that orders are filled by either conducting an auction that finds a seller or buyer, or, if necessary, filling orders from its own inventory.1 Each specialist centralizes liquidity for its listed companies - backed up by the commitment to use its own accounts to fill order - creating a self-contained, centrally-managed structure.