Where in North America is area code 650?

Wikipedia says "most of San Mateo County, California, (except the northernmost portion) and the extreme northwestern portion of Santa Clara County including Palo Alto, Mountain View, and Los Altos"

Area code 650 includes a tiny part of the city of San Francisco, plus the San Francisco International Airport. It also includes Redwood City, San Mateo, San Bruno, San Carlos, Belmont, Atherton, Colma, South San Francisco, Millbrae, Burlingame, East Palo Alto, Foster City, Menlo Park, Pacifica, San Carlos, and most of Daly City.

(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)