Initial provisional results of the presidential run-off poll, pitting former international footballer George Weah against Vice President Joseph Boakai, are expected to be announced on Thursday, the National Electoral Commission (NEC) said on Facebook.
Back in 2003 Sirleaf's predecessor Charles Taylor had fled the country with hopes of avoiding prosecution for funding rebel groups in neighbouring Sierra Leone, while two presidents who served prior to Taylor were assassinated.
The tumult of the last seven decades in Liberia, a small west African nation where an estimated 250,000 people died during back-to-back civil wars between 1989-2003, means a democratic handover has not taken place since 1944.
"No matter the results, we will accept it without causing problems. We don't need trouble here anymore," said Samuel Nuahn, 46, who voted for establishment candidate Boakai in Tuesday's run-off.
UN Secretary-General Antonio Guterres hailed the "peaceful conduct" of the second round vote, commending in a statement "the government, political parties and the people of Liberia for the orderly poll."
The Economic Community of West African States (ECOWAS) praised the peaceful nature of the vote
While the NEC did not indicate what time it could start releasing results on Thursday, local media was already saying Weah, the only African ever to have won FIFA's World Player of the Year and the Ballon D'Or, was ahead.
As observers hailed a credible election held without a single major incident of violence, despite weeks of delays caused by legal challenges, Liberians said they were looking forward to the baton of peace held for 12 years under Sirleaf being handed over.
"Since years of civil war this is the first time we see the transition of power from one person to another. So today is an exciting moment for me especially as well as an exciting moment for Liberia," voter Oscar Sorbah told AFP after casting his ballot on Tuesday.
The Sirleaf administration, elected in 2005, guided the nation out of the ruins of war and through the horrors of the 2014-16 Ebola crisis, but is accused of failing to combat poverty and corruption.
Weah's CDC party watched their icon miss out on the presidency in a 2005 bid and was similary frustrated when he ran for vice-president in 2011, but has repeatedly urged its young and exuberant supporters to keep cool.
"No matter what the provocation will be, CDC will not respond with violence," Jefferson Kotchie, head of the youth wing of the CDC, told supporters assembled at the headquarters of the party.
The run-off vote was delayed for seven weeks due to legal challenges lodged by Boakai's Unity Party against the electoral commission over the conduct of the first round, but many of the complaints appeared to have been addressed in the second round.