Following the Civil War, counterfeiting of US currency was a huge problem. Apparently, almost half the money in circulation at the time was counterfeit! The
Secret Service was created as a branch of the Treasury Department to combat this counterfeiting ... in secret. President Lincoln established the United States Secret Service on April 14, 1865, and who knows ... maybe he even named them the Secret Service :wink: Sadly, Lincoln was assassinated later that day. It wasn't until 1901, after the assassination of President McKinley, that the Secret Service was tasked with protecting US Presidents.
In 1867, the Secret Service expanded into "detecting persons perpetrating frauds against the government, " which included investigating "the Ku Klux Klan, nonconforming distillers, smugglers, mail robbers, land frauds and a number of other infractions against federal laws."
The Secret Service has two missions ... one is the protective services, while the second is investigating financial crimes. That includes investigating counterfeiting, forgery, and theft of US money and securities, as well as fraud (credit card, telecommunications, computer, and identify).
The Secret Service uniform varies depending on the agent's responsibility. Agents on protective detail may wear business suits (like all those guys in suits surrounding the president), or any other attire one would wear to blend in (surfer dude agent anyone?). Plainclothed (civilian clothed) Secret Service agents wear a little pin on the lapel that identifies them to other agents as Secret Service, rather than that big splashy I'M A SECRET SERVICE DUDE on a vest. Uniformed officers, like those in the photos above, wear standard police or utility uniforms. Which of course, includes the ballistic/identification vests that say Secret Service.
Interesting little tidbit. The FBI was created from the Secret Service.
So ... there you have it. The Secret Service may not be quite so secret anymore, but many agents on duty are indistinguishable from the rest of us. Even wearing jeans and a jacket. And ... they wear sunglasses just like the rest of us, to keep the sun out of their eyes