There are 801 "wi-fi", or wireless fidelity, points in San Francisco where people with laptop computers can get broadband connections to the internet, according to JiWire online hot-spot directory based in South San Francisco.
While San Francisco topped the United States, it ranked fifth in the world behind Paris, London, Tokyo and Seoul.
On Tuesday, JiWire listed 2056 wi-fi spots in Seoul and 1802 in Tokyo. The directory had 1627 hot spots in London and 950 in Paris.
New York City came in second in the United States with 643 hot spots and Chicago ranked third with 501.
Technology for the masses
David Blumenfeld, vice president of marketing at JiWire, told AFP: "While we can't claim to have every single hot spot under the sun listed, we feel this is a true representation of what is out there.
"Wi-fi is here and is a viable technology for the masses. Which is why you see a push to broad-scale wi-fi networks throughout the world."
The San Francisco Bay area, abutting Silicon Valley, is a techno paradise rife with "early adopters", people quick to embrace new innovations, Blumenfeld said of the prevalence of wireless spots there.
There has been a huge effort to mobilise wireless broadband connections in South Korea and Japan, which are among the Asian countries ahead of the United States when it comes to wireless technology.
"You could make the case that with wi-fi on the scene, it is a much cheaper way to get broadband to the masses than having to run a lot of fixed lines," Blumenfeld said.