AMERICAN INTERIOR is a documentary of Welsh musician Gruff Rhys - of the band Super Furry Animals - on his Investigative Concert Tour™ of the titular location retracing the steps ancestor John Evans (realized here as a felt puppet), the son of hillside farmers motivated by contact with opium-addicted poet/revolutionary Iolo Morgannwg to go to America in search of the lost tribe of Welsh-speaking Native Americans descended from ancient Welsh prince Madog who was believed to have discovered America in the twelfth century. The legend of this tribe embodied the idea for eighteenth century Welsh of an untarnished people and the possibility of a fresh start in the New World. Evans arrived in America and converted from Methodist to Baptist and learned cartography before moving westward. In order to cross over to the Spanish-dominated Western territories, he became a Spanish citizen which allied him with the Spanish and French against the Americans as well as the British. After being imprisoned by the Spanish under suspicion of being an American spy, he would be appointed second-in-command of an expedition to map the Missouri and discover a portal to the Pacific Ocean lead by James MacKay since it was felt that his ability to speak the Welsh language would ease tensions with the warring tribes along the river. Although he would meet many Indian tribes in mapping 1,800 miles of the Missouri - including the Mandan of North Dakota of which only a few thousand are now left (with only one native speaker of the language) - he never found evidence of any Welsh-speaking tribes, making him unpopular with his fellow countrymen. He would die at the age of twenty-nine under house arrest of the Spanish governor in Louisiana. Although he never found the lost tribe, Evans' map would be used by Lewis and Clark on the first year of their expedition; and thus, in the geography of what would become the United States. Following Evans' route, Rhys tour provides audiences members with a PowerPoint presentation and a short film by historian Gwyn Alf Williams on Evans, semi-comic biographic information on his upbringing in the shadow of his ancestor, and an insight into his working methods as he develops songs about the experience. The journey not only builds a portrait of America over two hundred years ago compared to how it is now, but also an exploration of Welsh culture in the United States and its survivals in place names and the language as spoken by both those of Welsh heritage and enthusiasts.