The oil-rich, mainly Christian south is widely expected to secede from the mainly Muslim north, splitting Africa's largest country in two. The north has promised to let the south go peacefully.RELATED:As vote looms, S. Sudan and renegade general reconcileGetting ready for Africa’s newest country?"This is the historic moment the people of Southern Sudan have been waiting for," said Southern Sudan President Salva Kiir as he cast his vote in front of a cheering crowd of hundreds lined up in front of the polling station. Sudan activist George Clooney and US Sen. John Kerry were on hand to watch Kiir vote.Kiir, wearing his trademark black cowboy hat, appeared visibly emotional as he remembered the 2 million people killed in 1983-2005 civil war. He also honored rebel leader John Garang, who died in a plane crash shortly after the peace deal was signed."I am sure that they didn't die in vain," he told the crowd. Women broke out in singing and chants and one man waved a sign saying: "A road toward sovereignty. A new nation to be born on the African continent!!!"Many voters lined up in the middle of the night, and some slept at the site of Garang's grave, where Kiir voted. Among the voters was Mawien Mabut, a 36-year-old soldier who was grinning widely as he lined up to cast his ballot."I have seen the inside of war so we have to stop the war now. We are very happy the Arabs are going away," he said.Standing near him was Rachel Akech, 30. The tall, pregnant woman has traditional scars on her face and her lower teeth removed, a tradition in the Dinka tribe."I couldn't even sleep I've been thinking about this day for so long," she said. "I am ready to vote."This week's referendum is part of a 2005 peace deal that ended the two-decade civil war between the north and south. Voters can mark one of two choices — a single hand for independence or two clasped hands for unity. The illustrations are necessary because only 15 percent of the region's 8.7 million people can read.Southerners, who mainly define themselves as African, have long resented their underdevelopment, accusing the northern Arab-dominated government of taking their oil revenues without investing in the south. Southern Sudan is among the world's poorest regions, and the U.N. says a 15-year-old girl has a higher chance of dying in childbirth than finishing school.Sudan will lose a third of its land, nearly a quarter of its population and much of its main money-maker — oil. In recent weeks the president of Sudan, Omar al-Bashir, has sought to play down fears of potential violence, saying the north will accept a vote for secession.About 117,000 southerners who live in the north also registered to vote, but the scene at one polling station in Sudan's capital of Khartoum was far removed from the joyous scenes in the south. Many southerners fear retribution from northerners if they vote.The north and south still need to negotiate the distribution of oil revenues, rights to the White Nile, official borders and citizenship rights. Full independence wouldn't take place before July 9, when the 2005 Comprehensive Peace Agreement, or CPA, expires and a new agreement must take its place.Clashes could still flare along border hotspots and in the disputed border region of Abyei. That region had also been scheduled to hold a freedom referendum on Sunday but its status is disputed by the two sides. It is likely to be subject to continued negotiations between the north and south, brokered alternately by the African Union and the United States.