Jetpac, a startup known for its beautiful "social travel" iPad app has been analyzing millions of Instagram photos to uncover all kinds of interesting things about life in the U.S.

For instance, it looked at pictures of people smiling and laughing to come up with this list of the 20 happiest cities in the U.S, posted below.

The list is surprising. St. Louis was crowned the happiest city, while Los Angeles didn't make the list at at all.

Jetpac has invented some big data technology to figure out things about Instagram pictures, like if the picture shows men, women or children; what the people are doing and how happy they seem to be while doing it. All of those things are really pretty hard for a computer to normally do.

On Thursday, the startup released a new iPhone app called City Guides that uses this data to show you the best spots in any city. (We've been using the app for a couple of weeks now and like it.)

Based on thousands of Instagram photos for each city, Jetpac says these are the 20 happiest places in the nation:

No. 1: Saint Louis, MO

No. 2: Kansas City, MO

No. 3: Columbus, OH

No. 4: Indianapolis, IN

No. 5: Pittsburgh, PA

No. 6: San Antonio, TX

No. 7: Minneapolis, MN

No. 8: Jacksonville, FL

No. 9: Detroit, MI

No. 10: Raleigh, NC

No. 11: Nashville, TN

No. 12: Chicago, IL

No. 13: Charlotte, NC

No. 14: Baltimore, MD

No. 15: Tampa, FL

No. 16: Denver, CO

No. 17: Dallas, TX

No. 18: Phoenix, AZ

No. 19: Boston, MA

No. 20: Houston, TX