In his new book, Who Discovered America, Controversial historian Gavin Menzies claims that the Americas were discovered by a Chinese sailor and explorer Zheng He at least 70 years before Columbus ever set sail. Part of his theory is based on an old map that pre-dates European explorations. According to Menzies, Zheng landed around Peru then sailed south around the tip of South America and went as far north as the Mississippi River.
Menzies first put out his theory about Chinese exploration in his 2008 book 1421 and has generated at lot of controversy among historians. Regardless, a good old-fashioned mystery about the past is always a fun read.