The Secret Service has existed as a federal agency for more than 150 years, but its role to protect national leaders and visiting heads of state was not its original purpose. The agency was founded in 1865 as a bureau in the Treasury Department to combat the growing use of counterfeit currency at the end of the Civil War and still works to safeguard the nation’s financial infrastructure, according to the United States government.

Following the assassination of President William McKinley, Congress requested Secret Service protection of U.S. presidents. In 1908, the service’s protection grew to provide protection for the President-elect and again in 1965 to include former presidents and their families. In recent years, the cost of protecting first families has generated controversy.