Nairobi is the capital and largest city of Kenya. The city and its surrounding area also form Nairobi County. The name "Nairobi" comes from the Maasai phrase Enkare Nairobi, which translates to "cool water". The phrase is also the Maasai name of the Nairobi river, which in turn lent its name to the city. However, it is popularly known as the "Green City in the Sun" and is surrounded by several expanding villa suburbs. Inhabitants of Nairobi are called Nairobians, and the city is governed by the County Government of Nairobi, whose current governor is Evans Kidero.
Nairobi was founded in 1899 as a rail depot on the Uganda Railway. The town quickly grew to replace Machakos as the capital of British East Africa in 1907. After independence in 1963, Nairobi became the capital of the Republic of Kenya. During Kenya's colonial period, the city became a centre for the colony's coffee, tea and sisal industry. Nairobi is also a county in itself. The city lies on the Nairobi River in the southern part of country, and has an elevation of above sea level.
With a population of about 3.36 million estimated in 2011, Nairobi is the second-largest city by population in the African Great Lakes region after Dar es Salaam, Tanzania. According to the 2009 census, in the administrative area of Nairobi, 3,138,295 inhabitants lived within . Nairobi is the 14th-largest city in Africa, including the population of its suburbs.
Nairobi is one of the most prominent cities in Africa, both politically and financially. Home to thousands of Kenyan businesses and over 100 major international companies and organisations, including the United Nations Environment Programme (UNEP) and the main coordinating and headquarters for the UN in Africa and Middle East, the United Nations Office at Nairobi (UNON), Nairobi is an established hub for business and culture. The Nairobi Stock Exchange (NSE) is one of the largest in Africa and the second-oldest exchange on the continent. It is Africa's fourth-largest exchange in terms of trading volume, capable of making 10 million trades a day. The Globalization and World Cities Study Group and Network (GaWC) defines Nairobi as a prominent social centre.
The area was essentially uninhabited swamp until a supply depot of the Uganda Railway was built in 1899, which soon became the railway's headquarters. The city was named after a water hole known in Maasai as Enkare Nairobi, meaning "place of cool waters". It was completely rebuilt in the early 1900s after an outbreak of plague and the burning of the original town. The location of the Nairobi railway camp was chosen due to its central position between Mombasa and Kampala. It was also chosen because its network of rivers could supply the camp with water and its elevation would make it cool enough for residential purposes. However, malaria was a serious problem, leading to at least one attempt to have the town moved.
In 1905, Nairobi replaced Mombasa as capital of the British protectorate, and the city grew around administration and tourism, initially in the form of big game hunting. As the British occupiers started to explore the region, they started using Nairobi as their first port of call. This prompted the colonial government to build several spectacular grand hotels in the city. The main occupants were British game hunters.
Nairobi continued to grow under the British and many British subjects settled within the city's suburbs. In 1919, Nairobi was declared to be a municipality. In February 1926, E.A.T. Dutton passed through Nairobi on his way to Mount Kenya, and said of the city:
After independence, Nairobi grew rapidly and this growth put pressure on the city's infrastructure. Power cuts and water shortages were a common occurrence, though in the past few years better city planning has helped to put some of these problems in check.