"This has been an incredible experience. The people have been... this is the third time we've won. But this is the biggest one."
The former U.S. president won the state's caucus by a record-setting margin over his closest opponent - Florida Governor Ron DeSantis.
DeSantis edged past former UN Ambassador Nikki Haley after a tight race for second.
Both were aiming for a strong second-place finish to show voters and donors that their challenges to Trump remain viable.
With 95% of votes tallied, Trump had 51%, while DeSantis was at 21% and Haley 19%, according to pollster Edison Research.
Meanwhile, entrepreneur Vivek Ramaswamy quit the race after a poor showing in Iowa, and said he's endorsing Trump for president.
The state's Republican voters had braved life-threatening snow and cold to back Trump, despite him facing four criminal cases that could go to trial before the November 5th general election.
According to Edison Research, two-thirds of caucus-goers think Trump would still be fit for president if convicted of a crime.
Most also embraced Trump's falsehoods about voter fraud, with two-thirds saying they did not believe Biden legitimately won the 2020 election.
"I lived the high life in 2016 to 2020, so I'd like that life back. That's all."
"I don't think it took an oracle to know that we're just going through the motions and that President Trump is the nominee."
The state was a political battleground between the GOP and the Democratic Party that supported Barack Obama in 2008 and 2012.
But it's now seen as a reliably red state in presidential elections, with registered Republicans edging out Democrats.
