De San Francisco na memória Alpha , parece que a razão era histórica, tanto no universo ...:
Role in diplomacy
The city had a prestigious history as a place of peace. In 1945, the Charter for the United Nations was signed in San Francisco by some fifty of Earth's nation-states.
After World War III, the nations of the world met in San Francisco to negotiate a peace treaty. (ENT: "Demons")The spotlight of diplomacy fell on San Francisco again in 2155, when the representatives of Earth, Vulcan, Tellar, Andoria, Denobula, Rigel V, and Coridan met in the city to hold talks on the formation of a Coalition of Planets. (ENT: "Demons", "Terra Prime")
Six years later, in 2161, the charter that lead to the founding of the United Federation of Planets was signed in San Francisco. (ENT: "Zero Hour", "These Are the Voyages...")
... e off-the-set :
Gene Roddenberry established the city's importance to the Star Trek franchise with the production and novelization of the first feature-length film, choosing San Francisco primarily because of its role in the creation of the United Nations. However, he also considered the city an appropriate showcase for the secular Humanism that underlined much of his own philosophy.