The U.S. financial system processes millions of transactions each day representing daily transfers of trillions of dollars, securities, and other assets to facilitate purchases and payments. Concerns had been raised, even prior to the recent financial crisis, about the vulnerability of the U.S. financial system to infrastructure failure. These concerns about the "plumbing" of the financial system were heightened following the market disruptions of the recent crisis. This book outlines the changes to the supervision of key market infrastructure that are embodied in the Dodd-Frank Act, and how the associated systems are currently overseen and regulated.