Voters in Scotland made their choice Thursday -- remain part of the United Kingdom, or form their own independent nation.
Now, the counting of the votes begins.
Polls at more than 5,500 stations across 32 districts, from the remote highlands and islands to the big cities of Edinburgh and Glasgow, closed at 10 p.m. local time (5 p.m. ET). People still in line to vote at that time were allowed to cast ballots.
More than 4.2 million people registered to vote on the question: "Should Scotland be an independent country?"
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, in addition to Scotland.
"The people of Scotland have engaged in this conversation," Phil MacHugh, a spokesman for the "Yes" camp, told CNN on Thursday night. "They have really gone out there, found out the information that they wanted to know, and made that choice today."
Official results will be announced at a central counting location in Edinburgh as they come in through the night, with a final tally expected early Friday.
The counting officer for Edinburgh, Sue Bruce, explained just after 10 p.m. that each ballot will be double-checked, to verify each voter's decision. She said that she hopes to announce the final result for her district -- Scotland's second largest, after Glasgow -- by 5 a.m. local time Friday.
Addressing dozens of election workers, Bruce added, "I look forward to working with you during the course of the evening to deliver an accurate and transparent Edinburgh count in which you and the voters of Edinburgh can have full confidence."
How all of Scotland decides on this crucial vote is far from clear. A final poll of polls by the independent research organization ScotCen showed the "No" camp with a narrow lead on the eve of the vote, with 52% support.
A new poll, conducted Thursday, suggests that margin may have grown.
The research and consulting organization YouGov asked more than 1,800 people who voted Thursday in Scotland as well as 800 who cast postal ballots. A small but significant majority -- 54% to 46% -- said Scotland should remain part of the United Kingdom, according to the poll, which was not conducted for CNN.
Voting was brisk at one polling station in Glasgow as the polls opened Thursday, with many people voting on the way to work or before taking their children to school.
Bad weather or the sheer volume of votes cast could slow down the counting process. However, the weather forecast appears good so far -- important when some ballot boxes must be collected by helicopter, plane or boat from polling stations on distant islands.
A simple majority is needed for either side to claim victory.
Scotland's First Minister Alex Salmond, who has led the pro-independence "Yes Scotland" campaign, cast his ballot Friday morning in the village of Strichen, Aberdeenshire.
Labour lawmaker Alistair Darling, who has headed the pro-union "Better Together" campaign -- backed by the main parties in Westminster -- voted in Edinburgh, while former Prime Minister Gordon Brown, another pro-union campaigner, voted in the town of Kirkcaldy.
For the first time, the vote was extended to 16- and 17-year-olds living in Scotland. Nearly 110,000 people younger than 18 have registered to vote.
Voters in the referendum did not have to be British citizens; Commonwealth, Irish and EU citizens who live in Scotland and are registered to vote there can cast a ballot. However, Scots living outside Scotland do not have a say.
Nearly 790,000 people applied for a postal vote -- the largest volume of registration for postal votes ever in Scotland.