Answer: Secret Service

Long before the United States had a variety of so called “alphabet agencies” participating in foreign and domestic intelligence and counterintelligence operations, they had the Secret Service.

Although today we strongly associate the Secret Service with the highly visible protection detail that surrounds current and former national leaders and their families (the President, past Presidents, Vice Presidents, presidential candidates, visiting heads of state, foreign embassies, etc.), in its original incarnation, the Secret Service was specifically created to investigate currency fraud to protect the fledgling U.S. dollar.

Created in 1865, the Secret Service did just that (and continues even now to protect U.S. currency against counterfeit fraud), but the service quickly expanded to also perform domestic intelligence gathering, investigation of murders, bank robberies, other high profile crimes, and otherwise worked to help support undermanned federal services like the U.S. Marshals and assist local law enforcement agencies.

It wasn’t until 1901 when, after the assassination of President William McKinley, that Congress added presidential protection duty to the roster of things the Secret Service was tasked with. The organization continued to assist with a broad range of investigations until the creation of the Federal Bureau of Investigation in 1908.

Today, the responsibilities of the U.S. Secret Service are heavily focused on presidential protection and financial crimes like counterfeiting and securities fraud with the vast majority of its former duties delegated in the 20th century to organizations like the FBI, the Internal Revenue Service, and the Bureau of Alcohol, Tobacco, and Firearms.