Following his Appleton's guide, Michael Portillo makes a trip to the jewel in the crown of America's National Parks, Yosemite, to behold its towering granite cliffs, its giant sequoia trees and cascading waterfalls. He discovers how early conservationists fought to protect it in law and encounters a 'buffalo soldier' in the heart of the forest. In Berkeley, Michael uncovers a catastrophic event, which hit the city of San Francisco hard in 1906. He heads for the University of California's department of seismology to hear of a devastating earthquake and the inferno which followed it and to find out what's being done to secure the region against future damage.

In Stockton, Michael discovers tractor heaven and learns how caterpillar tracked vehicles were developed to work the deep peat soils of the Sacramento-San Joaquin delta. Continuing south through the heart of Silicon Valley, Michael visits a high-tech bar, where the waiters are robots. He discovers the origins of modern-day search engines and social media in a Californian institution founded by a railroad baron. At tech giant Intel, Michael glimpses the future on a test drive in an autonomous car.

At San Jose, the biggest city in the valley, Michael visits Japantown to meet members of a far eastern community who settled here peacefully during the 19th century but faced hostility during the mid-20th. He is then beaten over the head and body by youngsters a third of his age as he attempts to learn the martial art of kendo. A ride aboard the Roaring Camp and Big Trees Railroad takes Michael through groves of mammoth trees - the magnificent California redwoods. Emerging from the forest on a second vintage railroad, Michael hits the beach and takes to the waves - on a surfboard.