The earliest I have found is the one I posted before, from Brown, North Carolina Folklore: Sung by Dr. I. G. Green, Boone, Watauga Co., 1921-1922. (Posted 13 Mar 03, with words)

Somewhere there should be a printing of the song before 1921.

My grandfather knew the song and often whistled it; he was born in Chicago in 1874 and raised in Colorado in the 1880s-1890s and lived most of his life in New Mexico (thus the song known in the west).
Kendall is not alone (a couple of other posts above) in believing the song goes back a ways.