"We are advancing with unbridled optimism and lifting our citizens of every race, colour, religion, and creed," Trump continues.

He continues by touting America's record low unemployment rate.

Without his policies, he says "the world wold not be witnessing this great economic success".

"African-American youth unemployment has reached an all-time low," he claims.

"African-American poverty has declined to the lowest rate ever recorded," he says, adding that women filled the role of 72% of all jobs added to the economy.

Our Reality Check team are with us all night and are going through the claims with care...

Image source, Getty Images

"The days of our country being used, taken advantage of, and even scorned by other nations are long behind us," says Trump.

"We have rejected the downsizing of America's destiny."

"We have totally rejected the downsizing.

"We are moving forward at a pace that was unimaginable a few years ago. And we are never ever going back."

"Jobs are booming. Incomes are soaring, poverty is plummeting, crime is falling, confidence is surging," the US president said.

"Our country is thriving and highly respected again."

Donald Trump has approached the dais and is now speaking to the House of Representatives and the Senate.

He is speaking in the same chamber where he was impeached less than three months ago.

His supporters are chanting: "Four more years."

Let's hear what he has to say.

Image source, Getty Images

A group of around two dozen lawmakers are wearing purple to symbolise bipartisanship and unity following months of impeachment drama.

The colour is a mix of red and blue (the colours of Democrats and Republicans).

Get it?

The White House has provided a few sentences from Trump's speech tonight. Here's a preview of what he plans to say:

• "Three years ago, we launched the Great American Comeback. Tonight, I stand before you to share the incredible results."
• "We will never let socialism destroy American healthcare"
• "As we defend American lives, we are working to end America’s wars in the Middle East."

For the third year in a row, Democratic congresswomen are wearing white in honour of the suffragette movement that got women the right to vote in 1920.

Congresswoman Debbie Dingell was among those that tweeted images of the group.

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Several of the more left-wing Democrats have announced that they will skip Trump's speech tonight.

Congresswomen Alexandria Ocasio-Cortez of New York and Ayanna Pressley of Massachusetts - both members of the so-called "squad" of freshmen lawmakers - have said they won't go.

“The State of the Union is hurting because of the occupant of the White House, who consistently demonstrates contempt for the American people, contempt for Congress & contempt for our constitution,” Pressley wrote on Twitter. “I cannot in good conscience attend tonight’s sham.”

Ocasio-Cortez tweeted minute later: “None of this is normal, and I will not legitimise it".

Earl Blumenauer of Oregon, Steve Cohen of Tennessee and Frederica Wilson of Florida are all skipping Trump's speech for their third year in a row.

Al Green of Texas, Hank Johnson of Georgia and Bennie Thompson of Mississippi also say they're out.

Image source, Getty Images

Lawmakers in the Senate and House are both permitted to bring guests tonight, which are often picked to highlight issues they care about.

Here's a few of those attending:

• Hatice Cengiz, whose US resident fiancé Jamal Khashoggi was killed by Saudi agents inside one of the kingdom's consulate buildings in Istanbul

• Rowena Chiu, a British-Chinese woman who worked as an assistant to movie mogul and accused rapist Harvey Weinstein. She broke a non-disclosure agreement to claim that he attempted to rape her in a hotel room in Venice in 1998

• Courtney Wild, who accuses Jeffrey Epstein - the millionaire who killed himself in jail himself while awaiting trial - of multiple sex crimes

• Dr Dieter Martin Gruen, a 97-year old German-born American scientist who worked on the Manhattan Project which designed the atomic bomb dropped on Japan during WWII

• Nathan Law, a Hong Kong democracy activist

• Rushan Abbas, a Uighur human rights activist

• Andrea Chamblee, the wife of a journalist who was murdered along with four others when the Capital Gazette newsroom in Pittsburgh was attacked by a gunman

We were offered a taste of the president's themes tonight in a background briefing to reporters last week from a senior Trump White House official.

The official said the president’s key motif would be "the great American comeback", with an overtone of "relentless optimism".

Trump will talk up the US economy and accuse some in Congress of "unjust pessimism", said the official. His speech will also address the matter of lowering healthcare costs, with a jab at “socialism". The president will discuss what the administration calls "safe and legal" immigration, and sanctuary cities, US urban harbours for undocumented immigrants.

The official answered "no comment" when asked whether the speech would address North Korea or the coronavirus.

President Trump and his wife Melania have invited eight people as their special guests to watch the State of the Union, with each guest highlighting issues that the president will address in his speech to the nation.

Among them are:

• Tony Ranks, a military veteran who suffered from PTSD and became addicted to drugs before he learned new job skills and quit drugs

• Border Patrol Deputy Chief Raul Ortiz, who works on the Texas-Mexico border where Trump wants to build a wall

Image source, White House

• Jody Jones, whose brother was killed by an undocumented immigrant. Trump has called the relatives of people killed by illegal immigrants "Angel Families"

• Kelli Hake and her son Gage, whose soldier father was killed in Iraq by weapons the White House says were provided by assassinated Iranian general Qasem Soleimani

• Ivan Simonovis, a former police chief in Caracas, Venezuela, who was jailed for protecting protesters. After escaping in 2019, he came to Florida "where immigration agents welcomed him to the United States", the White House said

Image source, White House

Another guest rumoured to be attending is Juan Guaidó, the Venezuelan opposition leader vying to oust President Nicolas Maduro.

Rush Limbaugh, the conservative radio host who announced he has cancer yesterday, is also expected to attend, despite not being on the formal White House guest list.

Image source, Doug Mills-Pool/Getty Images

President Donald Trump will give his third - and possibly final - State of the Union address tonight.

It is actually required by the US constitution that the president "shall from time to time give to Congress information of the State of the Union, and recommend to their consideration such measures as he shall judge necessary and expedient".

This requirement has been interpreted differently in the 200 years since President George Washington delivered the first in 1790.

In recent decades the address has become one of the major media events of the US political calendar. President Lyndon Johnson used it to launch his Great Society programme to end poverty in America, Bill Clinton promoted his stalled plan for health reform and George W. Bush made his case for war against Iraq, labelling the regime part of the "axis of evil".

For Trump, he has used his two previous speeches to tout his record in office and use the platform for a re-election pitch.

This year, the theme of Trump's speech will be "the great American comeback", highlighting key election year accomplishments like economic and military strength.

The president's address comes less than one day before he is expected to be acquitted by the Senate in his impeachment trial on Wednesday. But while the impeachment probe has loomed large over Washington for the past few months, a White House spokesman said today that the word "impeachment" is not in Trump's remarks.

Image source, Alex Wong/Getty Images

While we wait to find out which candidate Democratic voters in Iowa like the best, it's also worth thinking about the Iowans who didn't take part in the caucuses.

Swing voters like store manager Joe Wacha and farmer Barry Christensen.

They both voted for Democrat Barack Obama in 2012 but switched their support to Republican Donald Trump four years later.

In the last election, more than 200 US counties flipped from supporting Obama in 2012 to backing Mr Trump - and 31 of those counties were in Iowa.

Joe and Barry both live in Howard County in northern Iowa. It flipped by 41 percentage points in 2016, the largest change in the US.

The BBC's Angélica Casas and Marianna Brady went there to ask if any of the 2020 candidates could convince them to back a Democrat again in November's general election.

The State of the Union address - Mr Trump's third - will begin in just under an hour.

Michigan's Democratic Governor Gretchen Whitmer will deliver the rebuttal, and Veronica Escobar, a member of Congress from Texas, will deliver another in Spanish.

Image source, Joe Raedle/Getty Image

Bernie Sanders has been speaking for the first time after early returns from Iowa came in.

So far, the Vermont senator looks to be in second place in terms of precinct-wins - trailing just behind Pete Buttigieg. But overall, he appears to have won more votes.

Still awaiting the final tally, Sanders has taken an upbeat tone, telling supporters his campaign will be in first place once the results are in.

But it's not clear if Sanders is referring to the popular vote or the number of caucuses won by the candidate. Only caucus wins have bearing on the number of delegates awarded to a candidate - the actual goal of the caucus and primary season.

Earlier on Tuesday, Sanders said he was "extremely disappointed" by the delay in Iowa results.

"I don’t know why, in 2020, it should take so much time," Sanders said. “I don’t think it’s fair to the people of Iowa, the people of America, or to the candidates or their supporters.”

Pete Buttigieg is already in New Hampshire ahead of next Tuesday's primary there - in a speech there, he couldn't hide his joy at what looks like a good result for him in the Iowa caucuses.

Image source, Getty Images

Shadow Inc was founded by veterans of Hillary Clinton's failed 2016 presidential campaign, and was hired to design an app that would make reporting results as easy as the click of a button - theoretically.

The work on the app began with less than two months to go before the Iowa caucus and was shrouded in secrecy during that time.

Anonymous sources at Acronym, the parent company that either owned on invested in Shadow (depending on whether company executives can be believed), told the New York Times, external that the project was so rushed that it did not have time to be approved by the Apple app store.

Had it been, it may have been easier to download and use.

Instead, users had to bypass their phone's security system, a difficult task for some of the elderly volunteer officials in Iowa.

It also had to be installed using two-factor authentication and PIN passwords, which were written down on paper at caucus sites.

Ultimately only about 25% of Iowa's 1,700 precinct chairs were able to download and install the app, a Democratic consultant told the Times.

Image source, Jessica Rinaldi/The Boston Globe via Getty Image

Maybe not.

Democratic spending on TV and radio ads in the state was led by billionaire Tom Steyer with a whopping $16.3m (£12.5m), according to analysis by Kantar Media/ Campaign Media Analysis Group.

Based on preliminary results, Steyer tied Congresswoman Tulsi Gabbard for last place, with less than 1% of the vote.

But that's not to say that spending doesn't help at all. After Steyer, the next two big spenders - Bernie Sanders and Pete Buttigieg - are also the top two finishers in Iowa, according to early results.

Sanders spent $10.8m and is sitting in second place, beaten only by Buttigieg, who poured $10.5m into the state.

Image source, Joshua Lott/Getty Images

If the Iowa caucuses ever end, we'll be looking at what happens next.

The caucuses are the formal start of the 2020 election season but there are still nine months ahead of us until Americans pick their president.

Here are four quick questions to give you a sense of what to look out for next.

What happens next?

In a week, the first primary will be held in New Hampshire, a tiny north-eastern state of only 1.3m people. Pete Buttigieg is already there, as you may have seen from his earlier press conference.

Unlike a caucus, where voters are expected to turn up at a few limited locations at certain times and stick around for a while, primary voters can just turn up at a polling booth and vote in secret. Then leave.

What are delegates again?

Delegates are key to the caucus results: the more votes a candidate gets in a caucus, the more delegates they are awarded.

Those delegates then vote for that candidate as the party's nominee for president in the summer convention.

How many delegates are there?

The number of delegates differs in each state, and is decided by a convoluted series of criteria. In California's primary, for example, there are 415 Democratic delegates up for grabs this year. In New Hampshire, it's only 24.

This year is a bit different. Any candidate would need to get at least 15% of the vote in any primary or caucus to be awarded delegates.

What is Super Tuesday?

It is the big date in the primary calendar, when 16 states, territories or groups vote for their preferred candidate in primaries or caucuses. A third of all the delegates available in the entire primary season are up for grabs on Super Tuesday, on 3 March. By the end of the day it could be much clearer who the Democratic candidate will be.

Image source, Saul Martinez/Getty Images

Some early reports of tonight's State of the Union suggest that Juan Guaidó - Venezuela's opposition leader - will be attending Trump's address at 21:00 local time.

The 36-year-old has been recognised as Venezuela's president by a number of heads of state, including the leaders of Brazil, Columbia and Peru as well as Donald Trump.

If Guaidó turns up tonight, he'd be given a high-profile platform to stoke his efforts to oust President Nicolás Maduro.

Read more about Guaidó here.