Following a referendum in January 2011, Southern Sudan voted overwhelmingly for independence. It was confirmed that nearly 99% of the voters in the referendum were in favour of dividing what was previously Africa's biggest country. The formal declaration of independence was made on 9 July 2011, six years after the peace deal, which led to the referendum, took effect.
The above map shows that the great divide across Sudan is visible even from space, as this Nasa satellite image shows. The northern states are a blanket of desert, broken only by the fertile Nile corridor. Southern Sudan is covered by green swathes of grassland, swamps and tropical forest.
Source: BBC News
Sudan is one of the largest countries in Africa with a land area of over 1.8 million km2 and an estimated population of over 35 million. It borders the Central African Republic, Chad, Egypt, Eritrea, Ethiopia, Libya and South Sudan. Its geography is dominated by the Nile and its tributaries. The capital, Khartoum is situated at the confluence of the White Nile and Blue Nile. Its land borders total 6,751 km with a coastline on the Red Sea of 853 km. The north of the country is desert with little rainfall and high daily temperatures. The Red Sea coastal plain receives winter rain. The terrain is generally a flat, featureless plain. The land elevation is from sea level to the highest point Jabal Marrah at 3,071 m. The official language is Arabic and some English is spoken.
More details can be found at CIA Factbook.