Khartoum is one of three sister cities, built at the convergence of the Blue and White Niles: Omdurman to the north-west across the White Nile, North Khartoum, and Khartoum itself on the southern bank of the Blue Nile.
Khartoum has a relatively short history. It was first established as a military outpost in 1821, and is said to derive its name from the thin spit of land at the convergence of the rivers, which resembles an elephant's trunk (khurtum).
Khartoum grew rapidly in prosperity during the boom years of the slave trade, between 1825 and 1880. In 1834 it became the capital of the Sudan, and many explorers from Europe used it as a base for their African expeditions.
Khartoum was sacked twice during the latter half of the 19th century -- once by the Mahdi and once by Kitchener when the Mahdi was ousted. In 1898, Kitchener began to rebuild the city, and designed the streets in the shape of the British flag, the Union Jack, which he hoped would make it easier to defend.