Dan Snow riding rapids through the Grand Canyon
While much of the US was being rapidly settled in the 19th century, large parts of the West remained unknown.
Determined to change that, Civil War veteran John Wesley Powell resolved to lead an expedition along the "impassable" Colorado River and into the unexplored Grand Canyon.
In rowing boats like those used by the 1869 Powell expedition, historian Dan Snow followed the route taken by the pioneers.
Along the way, they slept on beaches and encountered numerous rapids.
But taking the wrong line through a rapid can have disastrous consequences, as Dan and fellow team members Tom and Dougal discovered.
Operation Grand Canyon with Dan Snow, starts Sunday 5 January 2014, 2100GMT, BBC Two, or watch it for seven days afterwards on the BBC iPlayer.
02 Jan 2014