The Kensington Runestone is an ancient artifact discovered in 1898 in a farmer's field near Kensington, Minnesota. It is inscribed with runes, a form of writing used by the Vikings, and is believed to be evidence of a Viking presence in North America centuries
From Wikipedia
The Kensington Runestone is a slab of greywacke stone covered in runes that was discovered in Western Minnesota, United States, in 1898. Olof Ohman, a Swedish immigrant, reported that he unearthed it from a field in the largely rural township of Solem in Douglas County. It was later named after the nearest settlement, Kensington.