Ooo, I can finally answer a question here! Most of this comes from the Book Destiny of the Republic by Candice Millard.

I think it's important to realize how people at the time thought about those assassinations. Up until Lincoln, there was only 1 known attempt of presidential Assassination, that of Richard Lawrence failing hilariously to kill Andrew Jackson. There were two attempts made to kill Lincoln before Booth was successful. And when Booth did succeed, being in such close proximity to the Civil War, Lincoln's death was largely seen as a casualty of it. For the most part, the American public didn't think anyone would kill the President. The President was just a regular citizen chosen by his peers for a period of only a few years, not some lofty monarch ruling for life. It was almost a point of pride that they didn't have to care about protecting their head of state.

Back in the days of Garfield and McKinley the average Citizen had a pretty good chance of being able to meet the President in person. Most Presidents had a scheduled time in their day when they would just let people come into the White House and shake their hand. This is relevant in the case of Garfield. Charles J. Guiteau had actually "met" Garfield several times in that way before he killed him. Many people on Garfield staff recognized him as "That crazy guy who wanted to be the ambassador to France." Guiteau was a lawyer who basically lived his life on the run from various collections agencies, leaving town in the middle of the night to start racking up bills in the next. After surviving a boat crash in which everyone on the other boat died in a fiery explosion he took it as a sign from God that he should get into Politics. In those days the "Spoils system" was an accepted thing in American Politics. If you do something significant enough to help a Politician win, they'll give you a cushy job like Postmaster or Ambassador. Guiteau was convinced that his own contributions to Garfield's campaign were enough to warrant being the Ambassador to France or Austria. After Pestering Garfield and his staff in person for a month or two, and failing to get the appointment he thought he deserved, he shot Garfield once in the arm and once in the back while he was GETTING ON A TRAIN ALONE. The perception at the time placed the blame, not on an apparent lack of body guards but on the spoils system that made the gunman think he was entitled enough to pull the trigger. Chester A. Arthur Presidency is best remembered for dismantling that corrupt system of favors. (Additional off topic information: Garfield died ELEVEN WEEKS after he was shot. The bullet shot into his arm entered and exited his body intact, and the bullet in his chest ended in a relatively benign place. Modern medical speculation is that Garfield probably would have survived if he hadn't been operated on at all. It was the meddling of Dr. Doctor Bliss that killed Garfield.)

The Case of Mckinley was similar to Garfield, but it did have the desired result in the end. The President was mingling in a large crowd of people who had not been screened by any kind of security service. Czolgosz got up close and fired two shots to the chest and while Mckinley didn't die immediately, he did die of an infection 8 days later. It was only after McKinley's death that congress changed the Mandate of the Secret Service to protecting the President.

In the 8 years of his presidency, 4 attempts were made on the life of Barack Obama. In the first 120 years of the office of the President existing, only 6 attempts were made on the lives of any of those presidents (three of those attempts did succeed.) Back then they were probably right to think it wasn't necessary to guard the life of the President, but things are different now. It's no longer inconceivable that someone would want to kill the President, its happened too many times before.

As I'm currently working on a book about Garfield's assassination, I can give you some more details regarding the impact his assassination had. All this comes from the research for said book, from both current works as well as diaries, newspapers, etc from the era.

First off, remember that the nation was still very divided when Garfield was elected thanks to the Civil War and reconstruction. Many people didn't see any hope for repairing the great divide between the north and the south and Democrats and Republicans. In fact, even Lincoln's assassination was met with division and partisan political sentiments (heck, there were even Republicans who celebrated Lincoln's death).

But Garfield's assassination was different. First off, it took him a really, REALLY long time to die. And with the telegraph and telephone being widely used, updates about the president's condition went to every corner of the nation multiple times a day. And with each update, the nation became more unified with their eyes trained toward Washington. When Garfield finally passed, the whole nation mourned. North and South. Republicans and Democrats.

On top of that, the UK made official motions to mourn the president's passing, whereas Lincoln's assassination barely got mentioned in the papers. They flew flags at half mast, observed moments of silence, the whole nine yards. In fact, even though this the centennial anniversary of the defeat of the British in the Revolutionary War, the event passed with no hard feelings. But only five years earlier, Americans still treated the British as their oldest rivals. And vice versa.

Garfield's impact on the nation through death was so great, his is one of the only statues permanently installed in the Capitol rotunda. FDR isn't in there. Teddy Roosevelt isn't. But Garfield, who was president for less than a year and barely signed any laws or gave any speeches, is in there. Because by dying, he saved the union and set our nation on the course to becoming a world power. At least, that's how it felt for the nation at that time.

Why are there mostly no answers on this sub?