When were crop circles first discovered?

There is evidence of crop circles throughout the 20th century and even earlier, although the evidence becomes less robust the further back one looks.

There are eye-wtiness reports of crop circles on record which date back to the late 19th century, and many more throughout the early decades of the 20th. Some of these reports stem from scientific journals, some from the popular press and some from official documents such as the US Government research, Project Blue Book (1952-69).

There is claimed to be a photograph of a circle from the 1930s in an archived book about Sussex, England. The earliest readily available photograph of a clear circle is from Australia in 1966, although it is in reeds on top of a pond, which differentiates it from the usual phenomenon. The earliest image clearly showing a swirled crop circle on land is from 1976, and was photographed in Switzerland.