It is still unclear whether the newly re-elected president Barack Obama has won the key battleground state of Florida.
The vote in the state, which introduced the terms "hanging chads" and "butterfly ballots" to the masses in its historic 2000 presidential election, remained too close to call long after Republican challenger Mitt Romney conceded defeat.
Latest tallies show Mr Obama edging out Romney by about 45,000 votes, or 0.53 percentage points, out of a total of 8.27 million votes cast in Florida, with about 99 percent of the votes counted.
"It's 1:42am in the morning (6.42am Irish time) and I just heard there are still people voting in Miami-Dade County," tweeted Chris Cate, spokesman for Florida's Secretary of State, who is responsible for elections.
"Kudos to their commitment to voting!"
The head of elections for Florida's Miami-Dade County, which accounts for about 10 per cent of the state's 12 million registered voters, said final results would not be available until this afternoon.
Until then, it may not be clear whether Mr Obama won the state, which he carried in 2008.
At one church in Miami hundreds of voters were still in line when polls were due to close at 7pm (midnight Irish time).
"I believe that Obama is doing a good job and he's going to do a better job," said Michele Adriaanse (59) who arrived to vote at 6.30 p.m. and finally cast her ballot shortly before midnight.
"If we don't give him the chance, things will go back to how they were," she added.
Miami-Dade Supervisor of Elections Penelope Townsley told reporters the delay was due to "an extremely high volume of absentee ballots" and because long lines forced some precincts to remain open hours after their official closing time.
Florida accounts for 29 of the 270 votes in the electoral college a candidate needs to win the presidency. That is more than any other swing state.
Most recent polls had given Mr Romney an edge over the incumbent in Florida, where the economic recovery has been slower than in other states and long-term unemployment has reached record highs.
But registered Democrats outnumber registered Republicans in Florida by about 5 percentage points and Mr Romney faced multiple headwinds in the state.
A plan by Romney's vice presidential running mate, US Representative Paul Ryan, to change the Medicare health insurance program for seniors was among the factors often cited as holding back Romney's campaign in the retiree-heavy state.
Complaints about voting procedures, long lines to cast ballots, restrictions on early voting and some possible irregularities have been heard repeatedly across Florida.
There have been no claims of anything widespread or problematic enough to cast doubt on the credibility of the Florida outcome.