Born in Culpeper County, Virginia about 1770, when he grew up, he made his way to Missouri via Kentucky in 1798, settling in Franklin County. In 1798, he received two Spanish land concessions of about 800 acres. There, he farmed, hunted, and trapped. In 1809, he established a saltpeter mining operation.
In 1810 was hired by John Jacob Astor to join a Pacific Fur Company expedition. He traveled with the trapping party along the Missouri River, making their way to Fort Astoria, Oregon. When the group moved into Idaho, Day was left behind to attend to a sick member of the party named Ramsey Crooks. In the months that followed the two men suffered terribly with Day coming down with scurvy, fighting off a wolf attack, few supplies, and nearly starving. Defying the odds the two men continued on but would face another obstacle when they were robbed and stripped naked by Indians on the Columbia River near the mouth of the river that now bears his name in Eastern Oregon. Left to die, they survived the still cold and snowy in the mountains in the Spring as they continued westward along the Columbia River. Finally, they were rescued by members of the Astor party and arrived at Fort Astoria in April 1812.
Though he hadn’t fully recovered from this ordeal, Day was sent with Robert Stuart and his party who were on their way to St. Louis in June. However, two days into the trip, Stuart said that Day had was acting very strangely and was suicidal. Stuart then paid an Indian to return Day to Astoria, along with a letter that said: “a doubt of the reality of his madness, whether it was not pretended as an excuse from performing the Journey.” However, when the trapper arrived back to Astoria he appeared to be in good health and was not acting crazy.
In 1813 Fort Astoria and all other assets in the area were sold to the North West Company. Day then spent the next eight years hunting and trapping for the new company mainly in the Willamette Valley and the inland northwest. In 1820 he was at the winter camp of Donald MacKenzie in Butte County, Idaho. He died there on February 16, 1820 and was buried nearby.
His name is well-remembered as several places are named for him including two rivers, a county, two cities, a dam, a reservoir, and a national monument.
Day was tall with a “handsome, open, manly countenance.” At 40 years old, he was “a prime woodsman, and an almost unerring shot” with “an elastic step as if he trod on springs.” — Washington Irving, author
Trappers, Traders & Pathfinders (by Randall Parrish, 1907)