Sports wagering revenue reached $25.4m (£23.0m/€26.2m) in the month, up from $5.7m in September 2021 and also 76.4% higher than $14.4m in August of this year, according to the Iowa Racing and Gaming Commission (IRGC).
Of this total, $21.2m was attributed to online betting, while the remaining $4.2m came from retail wagering.
In terms of spending, the $200.2m wagered in September was down from $210.4m in the same month last year, but 63.3% more than in August this year.
Players spent $177.6m betting online, as well as $22.6m at retail sportsbooks across the state.
Breaking down the performances of individual operators, Diamond Jo in Dubuque and its FanDuel sportsbook led the way with $6.5m from a $43.2m handle.
Sister property Diamond Jo in Worth, which also has a FanDuel sportsbook, placed second with $3.6m in revenue from $23.7m in bets, followed by Wild Rose in Jefferson and DraftKings with revenue of $3.0m from $29.5m in bets.
The IRGC also revealed that regulated sports betting activity in June generated $1.7m in tax revenue during the month.