On September 10, 1967, the voters of Gibraltar were asked whether they wanted to pass under Spanish sovereignty or remain under British sovereignty, with their existing institutions and the right to self-determination preserved. They voted 12,138 to 44 to remain British, on a turnout above 95 per cent.
It was taken in 1704, by an Anglo-Dutch force during the War of the Spanish Succession. Spain ceded it in 1713, in the Treaty of Utrecht. The loss was never accepted. Spain raised the question at the United Nations through the 1960s, where the decolonization committee had pressed Britain to negotiate. Britain's position since the 1713 treaty, and its commitment since the 1960s, has been that it will not transfer sovereignty without the consent of the people there, which is the proposition the referendum was called to test.
Spain dismissed it. Madrid argued that the population had been altered by immigration under British rule, and that they were settlers rather than a self-determining people. Britain rejected that. The UN General Assembly passed resolutions criticizing the referendum as contrary to its own decisions on decolonization.
Two years after the vote, in June 1969, Spain closed the border crossing at La Linea, and it stayed shut for more than thirteen years. Telephone and ferry links were cut, families on either side were separated, and Gibraltar's economy, which had depended on Spanish workers crossing daily, had to be rebuilt around something else, which turned out to be financial services, shipping, tourism and later online gambling. The border fully reopened in 1985. Spain joined the European Communities shortly afterwards.
The United Kingdom and Spain have since tried several frameworks, including a declaration of joint sovereignty proposed in 2002, which Gibraltar rejected in a referendum with more than 98 per cent voting no. September 10 is Gibraltar National Day, and the vote of 1967 is the foundational date in its political calendar.