The Treaty on the Non-Proliferation of Nuclear Weapons is signed in Washington, D.C., London and Moscow by sixty-two countries.

The Treaty on the Non-Proliferation of Nuclear Weapons, commonly known as the Non-Proliferation Treaty or NPT, is an international treaty, the objective of which is to prevent the spread of nuclear weapons and weapons technology, to promote cooperation in the peaceful uses of nuclear energy, and to further the goal of achieving nuclear disarmament and general and complete disarmament. Between 1965 and 1968, the treaty was negotiated by the Eighteen Nation Committee on Disarmament, a United Nations-sponsored organization based in Geneva, Switzerland.

Washington, D.C., officially the District of Columbia and commonly known as simply Washington or D.C., is the capital city and federal district of the United States. The city is on the Potomac River, across from Virginia, and shares land borders with Maryland to its north and east. It was named after George Washington, the first president of the United States. The district is named for Columbia, the female personification of the nation.

London is the capital and largest city of both England and the United Kingdom, with a population of 8,945,309 in 2023. Its wider metropolitan area is the largest in Western Europe, with a population of 15.1 million. London stands on the River Thames in southeast England, at the head of a 50-mile (80 km) tidal estuary down to the North Sea, and has been a major settlement for nearly 2,000 years. Its ancient core and financial centre, the City of London, was founded by the Romans as Londinium and has retained its medieval boundaries. The City of Westminster, to the west of the City of London, has been the centuries-long host of the national government and parliament. London grew rapidly in the 19th century, becoming the world's largest city at the time. Since the 19th century the name "London" has referred to the metropolis around the City of London, historically split between the counties of Middlesex, Essex, Surrey, Kent and Hertfordshire, which since 1965 has largely comprised the administrative area of Greater London, governed by 33 local authorities and the Greater London Authority.