Atlanta is now No. 2 in the number of Facebook users in the U.S. More users than in Chicago or L.A.

Yes, you heard that right. That’s what the numbers say in a new demographics and statistics report released today from Washington-based istrategylabs. Check out the chart here with all the numbers.

According to the report, only New York has more Facebook users in the U.S.. Atlanta experienced a 142.4% increase in users from Jan. 4 to July 4, moving from sixth place to second. Curiously, Atlanta had the smallest growth in users of the social networking site among metro areas in the previous six months.

What the heck is going on? Why the explosive growth? What does this mean?

We’ll be looking deeper into the numbers. At minimum, however, it should be a wake-up call to Atlanta area professionals and small businesses that their customers are flocking to Facebook.

From my own perspective, I’ve seen a flood of middle-aged former co-workers joining Facebook in recent months. I’ve been wondering myself why there’s been such a surge.

The same report also found a 513% increase in 55-plus Facebook users nationally from Jan.  4-July 4, along with a declining growth rate among students.

Why do you think Facebook is so hot now in the ATL? Let us hear from you, especially if you’re new to Facebook.