On the GOP side, with 98 percent of precincts reporting, the race was called for the Texas senator, who won eight delegates. That's compared to Donald Trump's seven. Sen. Marco Rubio, R-Fla., won six.
In an enthusiastic -- and long -- victory speech, Cruz whipped up the crowd.
"Iowa has sent notice that the Republican nominee and the next president of the United States will not be chosen by the media, will not be chosen by the Washington establishment," he said.
Trump, on the other hand, took a more subdued and humble tone than he has thus far.
"We will go on to get the Republican nomination and we will go on to easily beat Hillary or Bernie," he told supporters before heading off to New Hampshire. "We finished second, and I have to say I am just honored."
Rubio, finishing close to Trump, did not pass up a chance to take a victory lap, making his speech early in the evening before any other candidate.
I am officially suspending my campaign. Thank you for all your loyal support. #ImWithHucK— Gov. Mike Huckabee (@GovMikeHuckabee) February 2, 2016
"This is the moment they said would never happen. For months, they told us we had no chance," he said. "They told me that I needed to wait my turn, that I needed to wait in line. But tonight here in Iowa, the people of this great state have sent a very clear message -- after seven years of Barack Obama, we are not waiting any longer to take our country back."
By 11:16 p.m. CST, the race had still not been called for the Democrats. With 96 percent of precincts reporting, Clinton and Sanders both won 21 delegates each. Former Maryland Gov. Martin O'Malley failed to win any before suspending his campaign, CBS News reported.
"I want to thank everyone who came out to our events and lent me their ear and everyone who went out to caucus for me tonight," O'Malley told supporters in an emotional concession speech.
Despite the dead heat, Clinton claimed victory, telling a crowd she was "breathing a big sigh of relief."
"It is rare that we have the opportunity we have now to have a real contest of ideas, to really think hard about what the Democratic Party stands for," she said. "I am excited about really getting into the debate with Sen. Sanders about the best way forward to fight for us and America."
Sanders acknowledged the tie, but still touted his come-from-behind campaign.
"Nine months ago we came to this beautiful state," he said. "We had no political organization, we had no money, we had no name recognition. And we were taking on the most powerful political organization in the United States of America. And tonight while the results are still not known, it looks like we are in a virtual tie."
"Liberty is alive and well," Paul told supporters in his victory speech.
A senior staffer for Carson tweeted early Monday evening that the candidate would be leaving Iowa early in that night to avoid bad weather.
Former Florida Gov. Jeb Bush, Former HP CEO Carly Fiorina, former Arkansas Gov. Mike Huckabee, Ohio Gov. John Kasich, New Jersey Gov. Chris Christie, former Pennsylvania Sen. Rick Santorum and former Virginia Gov. Jim Gilmore all failed to win any delegates.
Bush, Kasich, Christie and Gilmore all opted out of Iowa celebrations Monday night. Fiorina was a no-show for her own caucus night party, choosing instead to get a head start on New Hampshire that evening.
Santorum's campaign sent out a press release earlier in the evening promoting a 46 county tour of South Carolina, apparently forgoing New Hampshire.
Huckabee tweeted he was suspending his campaign around 9:40 p.m. CST.