About 465 to 470 million years ago, a meteorite struck near present-day Decorah, Iowa, creating a 3.5-mile (5.6 km) wide impact crater buried beneath the city's surface.
Although this highlight is named “Decorah Impact Crater Marker”, at the time of my most recent hike to this highlight, on August 2, 2025, there was no marker or monument nearby.
However, there is a large bronze medallion set in concrete marking the precise meteorite impact site located about 0.2 miles west-southwest of this highlight.. The marker can be found at GPS coordinates 43.31580, -91.77474. I have made this location a komoot highlight as well.
The bottom of the impact crater now lies about 300 feet below the marker due to geological changes that have occurred over the millennia following the meteorite strike.
The crater and its discovery are significant because it is one of fewer than 200 recognized impact structures on Earth. It has preserved a unique fossil record of ancient life, including the nearly 6-foot sea scorpion known as Pentecopterus decorahensis.