RE: Carnation Ice Cream
In answer to the original question, Carnation was a regional company based in Southern California. They did distribute some products nationally (i.e., canned evaporated and condensed milk and powdered milk drinks). They sponsored the Burns and Allen TV show to advertise the canned products. Other products were sometimes mentioned on LA-based TV shows.
Pet Milk (St. Louis), Borden (Columbus) and Sealtest (Chicago area) were likewise local-regional dairies with some national products. As with Carnation, they started out selling fresh milk and cream (mostly by home delivery) in a local area and expanded geographically with products less prone to spoilage. In addition, Sealtest expanded early on by franchising their brand with various local dairies starting in the Midwest. And, as their brand names because known outside their "home" territories, all the companies expanded by acquiring local dairy operations allowing them to sell fresh, as well as packaged, dairy products in new markets.