Final leg of the journey takes me back over the Colorado River, this time into California. The river used to be miles wide here, expanding over the flood planes around the border. Now it is a far more modest size, with much of the water Bing held in the dams upstream and supplied to irrigate crops throughout two states.

Yama was the main crossing for those attempting to reach the gold fields of south California. Many impoverished settlers were denied entry to the sunshine state and so settled in the area, something the local museums make much off.

Over the bridge you head across the sand dunes towards the mountains. The original road was single track, made of wooden planks and involved an horrendous trip of at least a day to traverse the ten miles, leaving the travellers rather shaken.

The route now passes the history of the world in Granite. All the motors lie events in the history of the universe, etched onto long tablets of stone. It's a remarkable achievement and very informative. I can help but think Donald Trump could do with a visit.