Jackson, age 20, signed with the A's for $95,000 on June 13 and reported for his first training camp with the Lewis-Clark Broncs of the short season Single-A Northwest League in Lewiston, Idaho, managed by Grady Wilson. He made his professional debut as a center fielder in the season opener on June 24 at Bethel Park in Eugene, Oregon, but was hitless in five at-bats. In the next game, Jackson singled in the first inning and homered in the ninth. In the home opener at Bengal Field in Lewiston on June 30, he hit a double and a triple. In his final game as a Bronc on July 6, Jackson was hit in the head by a pitch in the first inning, but stayed in the game and drove in runs with two sacrifice flies. Complaining of a headache, he left the game in the ninth inning, was admitted to St. Joseph's Hospital in Lewiston, and remained overnight for observation.