And he grew up hearing stories about The Old West from family members. He established his reputation as a writer of The New West before he wrote Lonesome Dove–which includes bits of those old stories.
Zane Grey (January 31, 1872 – October 23, 1939) fits well into the old west time period.
But he grew up in Zanesville, Ohio. His dad a dentist.
I find his Westerns very fanciful and definitely fiction.
I second Laura Ingalls Wilder (February 7, 1867 – February 10, 1957) as the best example of authentic oral history. She documented her childhood on the prairies in great detail. Completely different life than the cowboys and gold miners often associated with the old west.