This is the Winter Solstice, the shortest day of the year. A very important time through most of human history, and marked in all kinds of religions. See a fascinating website about solstice at http://www.candlegrove.com/solstice.html .
When we lived in St. Louis, one of the most interesting places we explored was Cahokia Mounds, across the river in southern Illinois. This is one of the few remaining Indian mound sites in the region. The St. Louis area was so full of these mounds at one time that it was nick-named Mound City. But they have been bull-dozed or otherwise leveled and you would never know they had been there. But Cahokia is amazing.
Cahokia seems to have been the center of a mound-building culture that traded as far south as to reach the Aztec culture in what is new Mexico, and so far west as to reach the Pacific coast. The culture died out way before Europeans made it to the continent, and we don't know why that happened. They must have been a very wealthy and powerful people. Nobody knows for certain what the mounds were for. There are, however, remains of a wooden structure that seems to have been like a Woodhenge, marking the movements of the sun at solstice time.
I am pretty sure that there must have been folks out at Cahokia this chilly morning to welcome the sun at what had been Woodhenge or on the top of Monk's Mound, the tallest of the mounds. The image at the top is Monk's Mound, courtesy of http://www.state.il.us/hpa/Mounds.htm, which has a very nice, informative website about Cahokia. It's a great place if you are near enough, I recommend a visit. The interpretive center is very impressive, and the archeological work they have done and are still doing is great. They have wonderful brass doors on the center with bas relief ravens done by an artist, flying above the mounds. They are meaningful birds in the current Native American lore, according to what I was told. I like crows and ravens myself.