This diary recounts the day-to-day experiences of Thomas Flint, a young doctor from North Anson, Maine, who made two trips to California between 1851 and 1855. He travelled via Panama twice (including a return to Maine with 30-some pounds of gold), and finally returning to California overland, driving 2,000 head of sheep, cattle, horses and oxen, in partnership with his brother, Benjamin Flint, and cousin, Llewellyn Bixby. This became the basis for their founding Flint, Bixby & Co., and numerous subsequent business interests.

The main part of the diary covers the second trip to California, in 1853 and 1854, overland and driving a herd of livestock though the Illinois - Nebraska - Wyoming - Utah route to California. The detailed day by day entries describe distance, difficulties with the herds, crossing rivers, encounters with American Indians, Mormons, and other groups heading west on the same trail. It is full of very specific detail - daily logs of mileage, people they encounter, expenditures, income from trading along the way, and so on. Flint wrote "my pistol, whether awake or asleep was always at my right hand."

This is a reprint of the original edition published by the Historical Society of Southern California, edited by Waldemar Westergaard. The text has been reset, and there are additional introductory materials and notes.