John Day died February 16, 1820, at the winter camp of Donald MacKenzie's Snake Country Expedition in what is now the Little Lost River valley in Butte County, Idaho.
On February 16, 1820, John Day succumbed to his illness at the winter campsite of Donald MacKenzie's expedition through the Snake Country. This location is situated in the present-day Little Lost River valley, which lies within Butte County, Idaho.