Twenty years ago, when John McPhee began his journeys back and forth across the United States, he planned to describe a cross-section of North America at about the fortieth parallel and, in the process, come to an understanding not only of the science but of the style of the geologists he traveled with. The structural arrangement of the work never changed, but its breadth caused him to complete it in stages, under the overall title Annals of the Former World.

In Basin and Range, McPhee traverses the Basin and Range province, from Utah to eastern California, accompanied by Kenneth S. Deffeyes, a professor of geology who has done extensive field work in Nevada. In Suspect Terrain follows McPhee from the outwash plains of Brooklyn to Indiana's drifted diamonds and gold, in the company of the United States Geological Survey's Anita Harris, a Brooklyn native. In Rising from the Plains, he rides across Wyoming with David Love, a field geologist with a family history on the frontier and an unsurpassed understanding of Western geology. Assembling California takes McPhee across the Sierra Nevada and the Great Central Valley to the wine country of the Coast Ranges, the rock of San Francisco, and the San Andreas family of faults, with tectonicist Eldridge Moores as guide. In Crossing the Craton, a new and final essay and the last link in the cross-country chain, he and Randy Van Schmus, a geochronologist, explore the midcontinent's Precambrian basement.

Like the terrain it covers, Annals of the Former World tells a many-layered tale, and the reader may choose one of many paths through it, guided by twenty-five new maps and the "Narrative Table of Contents" (an essay outlining the history and structure of the project)