The Southern African Customs Union (SACU) is a customs union among five countries of Southern Africa: Botswana, Eswatini, Lesotho, Namibia and South Africa. Its headquarters are in the Namibian capital, Windhoek. It was established in 1910. History The SACU is the oldest existing customs union in the world. The first customs union in the area was established in 1889 between the British Cape Colony and the Boer republic of the Orange Free State. In 1891 British Bechuanaland and Basutoland joined, followed by Bechuanaland Protectorate in 1893 and Natal in 1899. Parallel to this process, the Boer republic of the South African Republic and Swaziland (then a protectorate of the South African Republic) formed a customs union in 1894. Following the Second Boer War, and the establishment of British control over the Boer republics, the Southern African Customs Union was formed in 1903 with the signing of a new Convention and replaced the previous arrangements. It consisted of Cape Colony (to which British Bechuanaland had been annexed in 1895), Basutoland, Bechuanaland Protectorate, Natal, Orange River Colony (the former Orange Free State), Transvaal Colony (the former South African Republic), and Southern Rhodesia. Swaziland joined in 1904 and North-western Rhodesia joined in 1905. In 1906 another convention was signed which superseded the 1903 agreement and retained all of the previous members. In its current configuration it was established in 1910 pursuant to a Customs Union Agreement between the Union of South Africa and the High Commission Territories of Bechuanaland, Basutoland and Swaziland. Southern Rhodesia and North-western Rhodesia (later to become Northern Rhodesia after 1911) had declined to join the 1910 Agreement but did maintain a common tariff and free trade arrangements with South Africa and the High Commission Territories (with some variations and exceptions) from 1910 until 1935. An attempt was made in 1949 to re-establish a customs union between South Africa and Southern Rhodesia, but it ultimately failed to do so. With the advent of independence for the High Commission territories, the agreement was updated and, on 11 December 1969, it was relaunched as the SACU with the signing of an agreement between the Republic of South Africa, Botswana, Lesotho and Swaziland. The updated union officially entered into force on 1 March 1970. After Namibia's independence from South Africa in 1990, it joined SACU as its fifth member, although it had been effectively a part of the customs union from the time