Harrison G. Rogers was Jedediah Smith's clerk on his two expeditions to California. He was killed in 1828, when most of Smith's party was massacred on the Umpqua River in Oregon. Smith, who escaped the massacre, returned to the Umpquas some months later with a party of the Hudson's Bay Company. He was able to recover some of his property, including the fragmentary remains of two of Roger's journals. These journals are now preserved in the collection of the Missouri Historical Society.
These journals were first published in:
The Ashley-Smith explorations and the discovery of a central route to the Pacific, 1822-1829, with the original journals, ed. by Harrison Clifford Dale. Cleveland : The Arthur H. Clark company, 1918.
This digital edition extracts the two Rogers journals from Dale: