In which country was frozen pizza invented?

According to Serious Eats, pizza was brought to the United States by Italian immigrants beginning in the early 1900s. CNBC reports that the treat began taking off in the early 1950s, preceded by refrigerated, ready-to-bake pies. The first mammoth frozen pizza manufacturer, Totino's, was founded in Minnesota in 1962, CNBC reports, followed by Mama Celeste's, Tombstone, and Red Baron brands.

Source: Tasting Table