Scotland's voters are headed to the poll Thursday to vote in a landmark referendum on independence from the United Kingdom, deciding whether to unravel a marriage with England that built an empire but has increasingly felt stifling and one-sided by a majority of Scots, the Associated Press reported. A simple majority is needed for either side to claim victory.

Today, the voters will face a straightforward yes/no question on the ballot paper: "Should Scotland be an independent country?"

Although months of campaigning have divided Scots, turnout in the referendum is expected to be high with more than 4.2 million people having registered to vote in the largest electorate ever in Scotland. For the first time, the vote has also been extended to 16- and 17-year-olds living in Scotland.

A vote for independence would mean Scotland, with its population of about 5.3 million, splits from the rest of the United Kingdom, made up of England, Wales and Northern Ireland.

The future of the 307-year-old union with England will be decided in 15 hours, with voting taking place from 7 a.m. until 10 p.m. local time (2 a.m. to 5 p.m. ET) at more than 5,500 polling stations across 32 districts nationwide, from the remote highlands and islands to the big cities of Edinburgh and Glasgow.

On a foggy morning in Scotland's capital, Edinburgh, voters lined up outside some polling stations even before they opened at 7 a.m. while many people voted on the way to work or before taking their children to school at a Glasgow polling station.

Since the "Yes" side of the campaign has energized young people and previously disillusioned working-class voters, nearly 110,000 people younger than 18 have registered to vote, CNN reported.

For elders, this was a day they had dreamed of for decades. "Fifty years I fought for this," said 83-year-old Isabelle Smith, a Yes supporter in Edinburgh's maritime district of Newhaven, a former fishing port. "And we are going to win. I can feel it in my bones."

"The one thing America has that the Scots don't have is confidence," said Smith, who returned to Scotland after living in the United States for three decades. "But they're getting it, they're walking tall.

"No matter what, Scotland will never, ever be the same again."

Meanwhile, many opponents of independence agreed that the campaign had reinvigorated Scottish democracy.

"I support the No side, but it's been a fascinating, worthwhile discussion about Scotland's future," said writing consultant David Clarke.

"If it's a No it's a win-win situation. If it's a Yes, we will have to deal with the fact that it's a Yes."

Chief Counting Officer Mary Pitcaithly is expected to announce the outcome "around breakfast time" after results from the different areas come in overnight into Friday morning local time.

Scotland's First Minister Alex Salmond, who has led the pro-independence "Yes Scotland" campaign, cast his ballot Thursday morning in the village of Strichen, Aberdeenshire. If the Yes side prevails he will realize a long-held dream of leading his country to independence after an alliance with England formed in 1707, according to the AP.

In a final speech on Wednesday night, Salmond told voters, "This is our opportunity of a lifetime and we must seize it with both hands."