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Remember those red equals sign profile pictures that were everywhere during the Supreme Court's gay marriage oral arguments in March? Facebook researchers dove into the data of those pictures on Monday, and found one surprising area that particularly loved those pictures and their pro-gay rights message: Missoula, Montana.

Using machine modeling, Facebook employee Bogdan State produced the map below of the 2.77 million users who updated their profile pictures to that ubiquitous red-and-pink symbol from the Human Rights Campaign. Facebook was able to accurately distinguish the true equals sign from its parody cousins, and it then mapped the rate of adoption onto the U.S. In the map below, the darker areas are where more people adopted the symbol. Each sectioned area holds 100,000 people, and the adoption rate ranges from more than 4 percent at its darkest to less than 1 percent at its lightest.

There are some obvious takeaways: The sign was less popular in most of the South, and more popular in the Northeast and pockets of big cities. One area that stands out is in Western Montana, surrounded by lighter colors in Big Sky country. Zoomed in:

That dark sliver is the population area surrounding Missoula, Montana, an area of heavy gay rights activism (on Facebook at least). Missoula is home to the University of Montana, attended by 15,000 students in a town of 67,000. President Obama win 58 percent of the vote in the county in 2012. Facebook's rougher analysis of the equals sign trend back in March found college towns to be the biggest adopters of the profile picture.