Although the U.S. Army allowed civilian aircraft to land at Vancouver Barracks beginning in 1905, military aircraft began operating here in 1921, when the U.S. Army Air Service established a landing field for an aviation forest patrol. The patrol was a cooperative forest fire spotting effort by the U.S. Army and the U.S. Forest Service. Two years later, the 321st Observation Squadron arrived at Vancouver Barracks, with three biplanes initially stationed at the field.
The 321st was a reserve training unit which participated in war games and reconnaissance operations, and even mobilized for emergency crop dusting in Oregon when apple orchards were faced with infestation.
Improvements in the form of hangars and the grading of the grass field occurred from 1924-1926, under the supervision of famed aviator Lt. Oakley Kelly. In September, 1925, the field was dedicated as Pearson Field, in honor of Lt. Alexander Pearson, Jr., an Army aviator who had been killed in 1924.
The 321st continued training operations into the 1930s, and was called to active duty in December, 1941, after which military flight operations were curtailed at Pearson Field.