Through July 31st, American Express is offering cardholders a $30 statement credit on purchases of $100 or more made in-store at Target or Walmart. Limit 5 statement credits (usually a one-time statement credit).
Log in to your American Express online account and scroll down to Amex Offers & Benefits. Click "Add to Card" to activate it. Some cardholders may not receive all offers (YMMV). Also, you generally need to be a cardholder in good standing for at least a few months to see these offers.
https://www.americanexpress.com/