Final answer:
Nelson Mandela was arrested and imprisoned after returning to South Africa from Algeria in 1964. He served a 27-year sentence, was released in 1990, and became South Africa's first Black president in 1994.
Step-by-step explanation:
After returning to South Africa from Algeria in 1964, Nelson Mandela was arrested and imprisoned. Mandela, a prominent leader of the African National Congress (ANC) and the anti-apartheid movement, was convicted for acts of sabotage and sentenced to life in prison. Mandela served 27 years of his sentence before he was released in 1990, following a period of domestic and international pressure on the South African government. The apartheid legislation was repealed, and following his release, Mandela went on to become South Africa's first Black president in the historic multiracial elections of 1994.