Is there a river that flows North that could be the River Sidon?  The Mississippi and Missouri do not fit the Book of Mormon's description of a river with its head waters (or beginning) up in the South (implying it flows North).  But the Grijalva River in Mesoamerica fits well.  There are many descriptions of radio carbon dating confirmed horses in the Americas well after the last ice age (about 10,000 BC), during Book of Mormon times (600 BCE to 400 CE)..