UPDATE — 2:15 a.m. ET: Prime Minister David Cameron reacted to the news that Scotland had rejected the independence referendum early Friday morning, saying he was pleased with the results.
"It would have broken my heart to see our United Kingdom come to an end," he said, adding that now is the time to "come together and move forward."
Cameron noted that "now the debate has been settled for a generation" and said "there can be no disputes."
"To those in Scotland sceptical of the constitutional promises made, let me say this: we have delivered on devolution under this government, and we will do so again in the next parliament," the prime minister said. "The three pro-union parties have made commitments on further powers for the Scottish parliament."
"We will ensure that they are honored," Cameron added.
Scotland voted on Thursday not to separate from the United Kingdom, rejecting an initiative to become an independent state and end the country's 307-year-old union with England.
Throughout the day, Scots turned out in record numbers to cast their ballots. More than 4 million individuals were registered to vote, including 16- and 17-year-olds, at the polls which closed at 10 p.m.
Supporters of the Yes campaign in the Scottish independence referendum cheer and wave Scottish Saltire flags after climbing up on the base of the Walter Scott Monument whilst awaiting the result after the polls closed, in George Square, Glasgow, Scotland, late Thursday, Sept. 18, 2014. (AP Photo/Matt Dunham)
Heading into the election, a Ipsos MORI poll suggested those in opposition to independence would ultimately edge out those in favor by a slim margin.
A YouGov prediction also indicated a victory for the No campaign by 54 percent to 46 percent.
Scottish Conservative leader Ruth Davidson told the BBC she was confident the "silent majority" of Scots would deliver a No victory, but the Yes campaign said it was too early to predict the outcome.
After polls closed, some No campaigners said they were confident they had swayed enough undecided voters to stave off independence. They may have been helped by a last-minute offer from Britain's main political parties to give Scotland more powers if voters reject secession, and by fears about the future of Britain's pensions and the National Health Service in an independent Scotland.
In this photo illustration, pound coins are placed on a Union Jack flag on August 20, 2014 in Glasgow, Scotland. First Minister Alex Salmond's, chief economic adviser has insisted Scotland has viable options for its currency if there is a yes vote in the independence referendum on September the 18th. (Jeff J Mitchell/Getty Images)
Had the referendum passed, it would have triggered 18 months of negotiations with the British government over how to split. Scotland would have then gained independence on March 24, 2016.
A cross marks a NO vote on a ballot paper at the count centre for the Scottish referendum at Ingleston Hall on September 19, 2014 in Edinburgh, Scotland. (Jeff J Mitchell/Getty Images)
British Prime Minister David Cameron is scheduled to deliver an address about the country's future Friday morning.
The Associated Press contributed to this report. This story has been updated.
Follow Oliver Darcy (@oliverdarcy) on Twitter