What is the happiest city in the U.S.? It's in North Texas

International Day of Happiness is just a week away on March 20 — you have that in your calendar, right? — and this year's theme is “Happier Together,” focusing on what we have in common rather than what divides us.

Researchers who study the science of happiness say that its key ingredients include a positive mental state, healthy body, strong social connections, job satisfaction and financial well-being. 

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So where do people check those boxes the most?

In order to determine where the happy people are in America, WalletHub compared more than 180 of the largest U.S. cities across 31 key indicators of happiness. The data set ranges from depression rate to income-growth rate to average leisure time spent per day.

Related: These are North Texas’ wealthiest ZIP codes

And Disney calling its California Disneyland park "The Happiest Place on Earth" might not be far off; the Golden State ranked five cities in the top 10 on the happiness chart.

Plano ranked first on the list, but California dominated the top rankings with Irvine at No. 2, Fremont No. 4, Huntington Beach at No. 5, San Jose No. 8 and San Francisco at No.10. 

Texas did have another top 10 city though: Grand Prairie ranked as No. 7.

Dallas and Fort Worth ranked as No. 68 and No. 42 respectively. Dallas lagged especially in the index's "Income & Employment" and "Community & Environment" rankings.

You can find out about how these cities match up with the cities where it’s most affordable to live and work by clicking here.

Other interesting findings:

• If spending hours in the car makes you crabby, move to Cheyenne, Wyoming, which has the lowest average commute time at 14 minutes. New York City has highest at 40.8 minutes.
• Soaking up some sun boosts your mood: Miami, Hialeah, Fort Lauderdale and Pembroke Pines, Florida all have the lowest depression rate at 12.50 percent. Charleston, West Virginia has the highest at 28.90 percent.
• Fremont, California, has the lowest separation and divorce rate, 15.96 percent, which is three times lower than in Detroit, the city with the highest at 47.44 percent.
• Motor City residents also get the least sleep: more than half of adults in Detroit sleep less than 7 hours a night, while in Overland Park, Kansas, nearly two-thirds of adults are getting adequate shut-eye.