In the mid-19th century, as much as half of American currency might have been fake. Money was kind of like driver's licenses -- many states were making their own, so it was relatively easy for counterfeiters to manufacture bills without being caught.

So on April 14, 1865, the Secret Service was created by President Abraham Lincoln. They would be the Treasury Department's army, tasked with fighting financial crime. Later that day, another blind spot in the federal government's layers of protection became obvious. The President was assassinated by John Wilkes Booth, and no one was there to prevent it from happening.

Two dead presidents later, Congress decided it might be prudent to make the Secret Service's duties, "protect money ... and the president." Teddy Roosevelt became the first president to have the full protection of the Secret Service.

The idea had some beta-testing before 1901, however. President Grover Cleveland had asked for protection from the Secret Service, and had a few detectives protecting him part-time over the course of his presidency. William McKinley succeeded him, and had similar protection. Guards were placed at the White House, and people milling around in the premises at the start of the 20th century were monitored for suspicious activity.

McKinley did not like this. Ten days before he was assassinated, the Washington Post printed a story about how the president wanted everyone to chill out. The American people loved him, and would never harm him, he said.

The story began:

President McKinley, both before and since his elevation to the Presidency, invariably objected to the employment of Secret Service men during public demonstrations, frequently saying to his intimate friends: "I have never done any man a wrong, and believe no man will ever do me one." ... At the urgent solicitating of his friends, he permitted one officer in plain clothes to accompany him on special occasions

Then there were rumors of an anarchist plot to kill him.

Mr. McKinley laughed at the report, characterizing it as a canard, and again expressing the belief that he was enough of the people to trust the people.

When he moved into the White House, he asked to have sentry boxes on the front lawn removed. He would go on walks around the White House by himself in the early morning. He would drive buggies around Washington unattended. The only Secret Service agent that Mr. McKinley seemed to like having around was an old man from Ohio named George Foster.

The article ended: "Capt. Vallelay told The Post reporter of his other experiences in guarding the President, and declared that absolutely no trouble of any sort was anticipated during the visit to Buffalo."

When the remains of President McKinley returned to the White House, he was accompanied by multiple Secret Service agents.

Teddy Roosevelt did not like the idea of being watched all the time, but he and those who followed in his place didn't have much of a choice. The New York Times wrote on September 29,

And thus the modern Secret Service was born. The job's proximity to the president made it somewhat of a dream job too, and the Treasury Department started getting lots of applications. Not all applicants were qualified for the job, such as the astrologist who argued he would have been able to protect the president by foreseeing his impending assassination.

Despite the Secret Service's new responsibilities, they were still tasked with looking into government fraud. During the 19th-century, they had investigated the Ku Klux Klan, mail robbers, and, of course, counterfeiters. During the Spanish-American War and World War I, they even did a bit of espionage. Over time, the Secret Service's purview in investigating fraud has grown broader as technology has advanced and laws have grown more complex. After the New Deal they began watching out for the Federal Deposit Insurance Corporation, and more recently, they have launched some high-profile missions against hacking, credit card fraud and identity theft. The Patriot Act gave the Secret Service the authority to partner with law enforcement and other entities to help suppress Internet crimes, as a Congressional Research Service report from earlier this year notes.

The aftermath of 9/11 also sent the Secret Service to a new home. After being wedded to the Treasury Department for over a century, the Secret Service was transferred to the Department of Homeland Security in March 2003. Since then, plenty of officials have wondered if the Secret Service should be divorced from its founding purpose forever. The Secret Service has been fighting to keep this role. As Marc Ambinder wrote in his great peek at the interworkings of the Service in 2011: "It may be true that if you designed the entire national-security apparatus from scratch, investigating financial crimes would fall outside the purview of the Secret Service. But from the agency’s point of view, its hybrid nature is a feature, not a bug."

Most Americans are likely oblivious to the fact that the Secret Service has any other face than the one it wears in public, the grim-with-glasses look of the men and women near the president. The Secret Service's responsibilities in this respect have grown astronomically too. After Robert. F. Kennedy's assassination in 1968, the Service began offering protection to presidential candidates. Former presidents were given lifetime protection -- which ended for a spell and has now been reinstated, despite budget concerns. Vice presidents and visiting foreign leaders are also offered extensive protection. If McKinley thought that having one or two Secret Service agents around was bad, he would have loathed the system in place today. When J.F.K. was shot in Dallas more than 50 years ago, there were around 38 agents present. Any big event Obama attends today requires hundreds of agents.

After the past few weeks of intense attention, the Secret Service is probably destined to change in new -- and big -- ways, but it seems doubtful that would mean a return to its earlier days, or a agency-wide reconsideration of the value of astrologists.

More more deep dives into the Secret Service, read:

This post has been updated.