Mo. Rev. Stat. § 452.075: Remarriage of former spouse ends alimony.

When a divorce has been granted, and the court has made an order or decree providing for the payment of alimony and maintenance, the remarriage of the former spouse shall relieve the spouse obligated to pay support from further payment of alimony to the former spouse from the date of the remarriage, without the necessity of further court action, but the remarriage shall not relieve the former spouse from the provisions of any judgment or decree or order providing for the support of any minor children.