What we know
Rock Island stop, established by 1902 (Place Names of Colorado).
Where it was
'Barnwell': Scott, Historic Trail Map of the Denver 1x2 Quadrangle (USGS I-2639, 1999, S-0106), symbol read from the reprojected sheet (good to a few hundred feet). Place Names of Colorado: Sec. 15, T10S R64W, 'Est. by 1902. Stop on CRI&P. 5 mi S of Elbert.'; this point is 0.69 mile from that section's center.
Read from Glenn R. Scott's USGS historic trail map of 1999 and confirmed by a second, independent source.
Sources
Sources are named in the text above. Numbers such as S-0080 refer to our source list. Most newspaper quotations were read in the Colorado Historic Newspapers Collection. Long quotations from recent books are shortened here.