Which agency is responsible for transporting prisoners between states?

The U.S. Marshals are specifically tasked with the transportation and management of federal prisoners between states. This includes the transfer of individuals who are awaiting trial or serving sentences, as well as those who need to be extradited from one state to another. The U.S. Marshals Service operates under the Department of Justice and has the authority to ensure the safe and secure transport of these individuals, thereby playing a crucial role in maintaining the federal justice system. This role is central to their mandate, which encompasses not only prisoner transport but also other law enforcement functions such as fugitive recovery and asset forfeiture. Other agencies, like the FBI or state police, while involved in various aspects of law enforcement, do not have the primary responsibility for the interstate transport of prisoners, making the U.S. Marshals the correct answer.