On the afternoon of November 19, 1863 - on the site of the American Civil War's bloodiest battle - US president Abraham Lincoln delivered a speech as part of the official dedication ceremony for the National Cemetery of Gettysburg in Pennsylvania.
The Gettysburg Address can be considered the most famous speech in US political history, and perhaps the most significant.
In its final sentence, President Lincoln said: "This nation, under God, shall have a new birth of freedom - and that government of the people, by the people, for the people, shall not perish from the earth."
Those are words redefining the meaning of war, setting out a view on how sacrifices to underpin freedoms are repaid by reinforcing democracy. The speech is inscribed on the wall of the south chamber of the memorial that bears his name. In the centre of the memorial is the enormous Georgia white marble sculpture of the man himself, who solemnly looks out over the Washington Mall, a concentration of major political and historical buildings that includes the White House, the Capitol - home to the House of Representatives and the Senate - and the Washington Monument.
Those buildings are where - over many decades - decisions have been made, for good and for ill, that have shaped the world we all live in. This is a serious place.
On Tuesday, Rex Tillerson was fired from the position of the US Secretary of State, the role of chief adviser to the president on foreign policy - or how America deals with the rest of the world. He learned this information by reading a tweet from Donald Trump. The Washington Post's front page lead story the next morning opened as follows: "Secretary of State Rex Tillerson was asleep in his Nairobi hotel room early Saturday morning fighting a stomach bug when White House Chief of Staff John F Kelly called to wake him around 2am to relay a terse message from President Trump: The boss was not happy. The president was so eager to fire Tillerson that he wanted to do so in a tweet on Friday but Kelly persuaded Trump to wait until his secretary of state was back in the United States from Africa, two people familiar with the conversation said."
Both Leo Varadkar and SDLP leader Colum Eastwood - to the best of my memory - drew a ripple of nervous laughter when they joked about Tillerson's exit in speeches at the public forum to mark the 20th anniversary of the Good Friday Agreement in the Library of Congress building on Tuesday night. It had been, as they pointed out, quite a day for American politics. On Thursday, after his visit to the White House, the Taoiseach would get a laugh at the reception at the Willard Hotel by referring to the entire episode as Rexit. Of course Tillerson's long-expected departure meant that, for every diplomat in every US embassy around the world, their boss had just been fired. Reece Smyth, charge d'affaires at the US Embassy in Dublin, was giving a speech as part of the Ireland Day Leadership Breakfast at the New York Stock Exchange on Tuesday morning as the Tillerson news broke. Life goes on.
Wednesday brought an invitation to the hugely-successful Ireland Funds Gala in the majestic setting of the National Building Museum. Flautist James Galway brought the house down when he finished the night with a rendition of Danny Boy. Hard to go wrong with Danny Boy and an American audience, he would admit himself. So he played it again at the White House during the St Patrick's Day reception the next day.
On the flight out to Washington, I had returned to a book I had been planning to read for quite some time. Bill Bryson's One Summer: America 1927 is heavily researched, insightful and wry, just like all of his bestsellers. I am, of course, late to the party (the book was first published back in 2013). Ironically, as I sat on my transatlantic journey, I read the opening chapter on Charles Lindbergh, the man who completed the first solo transatlantic flight (from New York to Paris) albeit in the opposite direction to which I was going. I was reminded that I had not been to the United States since being sent to New York on assignment about a week after the September 11 attacks in 2001. That had been a grim task. I remembered a city trying to get back to normal even as it was plastered in missing person posters. An exhibition of the original coverage of the atrocity can be seen at the Newseum on Pennsylvania Avenue in Washington - a news museum in effect, which highlights the importance of a free press and freedom of expression.
The Newseum also includes a humbling tribute to our own Veronica Guerin, who is remembered among those journalists who have given their lives while fearlessly reporting on matters of major public interest. Under the headline "Shot for her story", she is commemorated as follows: "Reporter Veronica Guerin investigated organized (sic) crime for Ireland's Sunday Independent. In 1996, she was shot and killed. Asked why she kept reporting on such a dangerous topic, Guerin said the criminals 'are destroying lives and they are practically untouchable'." In the glass case is a Montblanc pen she used to take notes, donated by her husband Graham Turley.
It takes something less than 20 minutes to walk from the Lincoln Memorial across Memorial Bridge - which spans the Potomac river - to the sombre surrounds of Arlington Cemetery. There, some 400,000 US soldiers and their relatives are buried, as are a number of political leaders, including, famously, John F Kennedy.
The iconic white rectangular gravestones stretch out all around you. This is the physical manifestation of the cost of decisions made about America and its place in the world. It is a cost paid by Americans and by those from many other countries. It is a cost paid by military men and women. It is a cost often paid by civilians - including on 9/11.
There is always a cost.
Just as at Gettysburg.
Abraham Lincoln knew that.