In the 1860 US Census Thornton was a farm laborer on the farm of Henry Reed. I found the following newspaper reference to Henry in 1867.
"Marysville Daily Appeal, Volume XVI, Number 79, 2 October 1867"
This likely narrows down exactly where Thornton was in 1860, "Reed's Ranch" in Dry Creek, West Bear River Township, Yuba County, California. G.E. Chittenden is listed in the 1860 US Census along with Henry Reed and Thornton and quite a few other farm laborers.