The book America Discovered by the Welsh in 1170 A.D. by Benjamin Franklin Bowen delves into the theory that the Welsh prince Madoc sailed to America in the 12th century, long before Columbus. Bowen examines historical documents, linguistic evidence, and cultural parallels between the Welsh and Native American tribes to argue that Madoc and his followers established settlements in what is now the United States. The book presents a detailed case for this theory, challenging the traditional narrative of America's discovery.