After beginning the 1903 season as a four–team league, the Southwest Iowa League expanded to a six–team league during the season. At a June 25, 1903 meeting, umpiring selection was taken over by the league, while the Creston Cyclones and a team from Osceola, Iowa were selected to join the league as expansion teams. The Shenandoah, Iowa franchise folded on July 18, 1903, weeks after winning the Southwest Iowa League first half championship with a 13–5 record. Shenandoah had a 22–14 overall record. The Creston Cyclones franchise permanently folded on August 29, 1903, with a 24–19 overall record. The Atlantic, Iowa team won the second half title and had the 1903 Southwest Iowa League best record, finishing 1st with a 34–26 record, 3.5 games ahead of the 2nd place Clarinda, Iowa team and 9.5 games ahead of the 3rd place Red Oak Blue Indians.
