Sunday was 906 Day, a day to celebrate Michigan's beautiful Upper Peninsula.

The 906 area code was established for the Upper Peninsula in 1961, separating it away from the 616 area code. It is to this day the least populous area code in the country, serving just 320,000 customers.

Every September 6, the residents of Michigan celebrate their northern half by posting beautiful photos from Michigan's wild UP.

I first went to the UP in 1977, and as an introvert, I fell in love almost immediately. Here's some place I could get away, and I mean really get away.

Among my favorite places in the Upper Peninsula are Canyon Falls, the Escarpment Trail in the Porcupine Mountains, and the remote Montreal Falls along the southern edge of the Keweenaw Peninsula at a place called Bete Grise Bay.

Here are some photos from social media celebrating this year's 906 day.