Crooked Creek crater in Crawford County, Missouri, is an exposed meteorite impact crater about 4.3 miles, or 7 kilometers, across. Estimated to have formed about 320 ± 80 million years ago during the Mississippian, it remains visible at the surface rather than being buried beneath younger sediments. Its circular form is part of the landscape itself. Crooked Creek is significant both as an impact site and as one of the so-called 38th parallel structures, a line of circular depressions across the central United States. That broader grouping has been proposed as a possible result of serial impacts, although that idea remains uncertain.