Who is responsible for investigating counterfeit money?

The responsibility for investigating counterfeit money falls primarily to the Secret Service. This agency was originally created in 1865 to combat counterfeit currency, as the production of counterfeit money posed a significant threat to the financial stability of the nation. The Secret Service's focus on financial crimes continues, and they are uniquely equipped with the resources and expertise to detect, analyze, and investigate issues related to counterfeiting.

The other agencies mentioned have different primary functions. While the Federal Bureau of Investigation addresses a wide range of federal crimes, including certain types of fraud, their jurisdiction does not center primarily on counterfeiting. U.S. Customs and Border Protection is tasked with managing and protecting U.S. borders, focusing on immigration and customs enforcement, not fraud or currency issues directly. Similarly, the Bureau of Alcohol, Tobacco, Firearms, and Explosives deals with regulations surrounding firearms, explosives, and illegal trafficking of alcohol and tobacco rather than currency crimes. This clear delineation of responsibilities underscores why the Secret Service is the correct answer.