Easily the oldest historic site in Minnesota, the first petroglyphs (rock carvings) on Red Rock Ridge in Southwestern Minnesota were produced between 7000 and 9000 years ago. Since the most recent were produced at late as 1800, some people consider Jeffers Petroglyphs to be the longest continually used sacred site in the world.
The petroglyphs were carved on the same Sioux Quartzite formation that forms Pipestone and Blue Mounds. According to the Minnesota Historical Society, the American Indians who created the pictures believed that places where this rock emerged from the prairie were spiritual places of connection - a link between the spiritual and physical world.
The images are incredibly hard to make out on the stone, especially on a rainy day like when I was there, but interpretive signs outline them decently. And apparently you can go out with a guide, but I missed that part. Even self-interpreted however the site really is amazing. It is crazy to think about people on this same rock creating the images I'm looking at 9000 years ago - before the pyramids were built, when mammoths still roams the plains. A mammoth could have stepped on these drawings and I'm looking at them. Talk about a link to the past.
The Jeffers Petroglyphs site also has a small section of virgin prairie - a rarity in Minnesota. It might be worth exploring the trails through the prairie, but since it was pouring rain, I forwent that pleasure. This is another must see Minnesota road trip site.