While New York, Los Angeles, and Chicago may lead in terms of population and prestige, San Francisco is the leader in a more modern category: official tourism Twitter account followers.

What’s your favorite city to follow on Twitter? If you chose San Francisco (@onlyinsf), you’re one of the 99,000-plus followers that made it No. 1 among the 10 most popular U.S. cities on Twitter.

New York City (@nycgo) and Las Vegas (@vegas) come in second and third while Los Angeles (@discoverLA) takes eighth place. Cities were ranked by the number of people following their official tourism Twitter accounts, not city government or other Twitter feeds.

The rest of the top 10 cities:

4. Miami (@miamiandbeaches)
5. Philadelphia (@visitphilly)
6. Chicago (@choosechicago)
7. Portland, Ore. (@travelportland)
9. Columbia, S.C. (@columbiasc)
10. Louisville, Ky. (@justaddbourbon)

The report from Skift, a newish New York company that produces travel information and news, looked at how tourism agencies use social media. During a two-week period, it found that Portland and Philadelphia were most responsive to answering questions via Twitter, and that New York City, Las Vegas and Portland had the quickest average response times to their tweets.

Does Louisville get a prize for having the most clever Twitter handle of the top 10? I want to know several things about these Twitter accounts:

1. How does the number of Twitter followers translate into tourism dollars? Tourism is big business for all of these cities so they have an interest in having engaging Twitter accounts.

2. Are most of these followers looking for special deals? Do they tend to follow the city when they already have a trip planned?

3. This doesn’t necessarily line up with one recent measure of the leading American cities for tourists. According to 2009 data listed by Forbes, here are the top tourist cities:

Orlando, Fla.: 48 million visitors
New York City: 47 million visitors
Chicago, Ill.: 45,580,000 visitors
Anaheim/Orange County, Calif.: 42,700,000 visitors
Miami, Fla: 38,100,000 visitors
Las Vegas, Nev.: 36,351,469 visitors
Atlanta, Ga.: 35,400,000 visitors
Houston, Texas: 31,060,000 visitors
Philadelphia, Pa.: 30,320,000 visitors
San Diego, California: 29,600,000 visitors

This data plus the Twitter data could be interpreted in a few ways. One way to view it is that some cities don’t need much of a Twitter following. For example, I assume Orlando and Anaheim get so many visitors due to the Disney presence. Thus, these visitors care a lot less about the cities (are there many people looking to get to downtown Orlando or Anaheim?).

4. Any chance these Twitter accounts take advantage of fake followers to improve their image? Boosterism may know few bounds…