The United States Secret Service (USSS) is a federal law enforcement agency charged with protecting the President of the United States.
The US Secret Service serve under the U.S. Department of Homeland Security. Until 2003, the Service was part of the U.S. Department of the Treasury because the organization's first mission was to fight counterfeiting of U.S. currency which was rampant following the U.S. Civil War. They currently have two distinct areas of responsibility, the other being protection, by ensuring the safety of current and former national leaders and their families, such as the President, past Presidents, Vice Presidents, presidential candidates, visiting heads of state, and foreign embassies.
The Secret Service are first shown with President Jefferson Rooney at an estate owned by zillionaire Ron Forester. They are neither able to prevent nor realize when Lucifer arrives and takes possession of the President. When a male aide ends up dead from massive cerebral hemorrhage, the Service agents gather around the President to pray for the fallen man.
Lucifer orders the leader, Rick Sanchez, to keep an eye out for two "mentally unstable individuals" who plan to assassinate the President. Lucifer wants the Secret Service to capture them. Rick accepts the order.
Rick and some members encounter the unstable individuals on the road towards the estate. Before they can arrest Sam and Dean though, Man of Letters Arthur Ketch knocks them out by blowing up one of their vehicles with a grenade launcher.
When the President's aide Kelly Kline asks to meet with the President at a hotel room, Lucifer sends a few agents to search the place. One finds Castiel inside a closet, but Castiel manipulates him into telling Lucifer the room is "all clear".
After Sam and Dean successfully exorcise Lucifer from the President, the Secret Service agents along with Rick find them crouching over an unconscious President, and proceed to arrest them and take the two to Site 94, on charges of attempting to assassinate the President as Lucifer predicted.
After two months, Sam and Dean manage to escape from Site 94. Rick and the Secret Service agents prepare to hunt them down along with Agent Camp. They are surprisingly overwhelmed by Sam and Dean, however. The brothers choose to spare them and inform Rick that they had rescued the President from the Devil.
Unfortunately for everyone present at Site 94, Arthur Ketch considers them all as loose ends and proceeds to kill each one of them.
Arthur eventually reveals the murder of the Secret Service agents while speaking to Mary Winchester.