When Bayard Winthrop, the chief executive of the retailer American Giant, ordered the batch of shirts that his company would advertise for the Fourth of July, he didn’t think much of it. The retailer, which has been producing its apparel solely in factories around the United States for more than a decade, perennially leans into its “Made in America” pitch for Independence Day.

This year’s batch of crew neck T-shirts are fittingly available in red, white or blue with very little embellishment other than getting straight to the point: Letters that read “American Made.” They cost $60 each. And they sold out in the first day. Then he ordered another set, which also sold out quickly as well. The company is scrambling to secure its fourth order.