On July 1, 1997, the United Kingdom handed back control of Hong Kong to China. This event, known as the "handover," signified the conclusion of 156 years under British rule. The shift occurred after a 99-year lease for the New Territories, which began in 1898, had expired. The Sino-British Joint Declaration outlined the terms of this transition. It introduced the "one country, two systems" concept. This allowed Hong Kong a high level of self-governance for half a century.