Just in case you were wondering, the herring catch was crucial to economic prosperity of merchants in the market towns of the Hanseatic League of the North Sea.
Atlantic herring was and is an important food to many Europeans. It's high in Omega-3 fatty acids and lends itself to preservation via pickling, fermentation, drying, and smoking. Pickled herring in particular are popular in Scandinavian, Dutch, Nordic, Polish, Baltic, and Jewish cuisines. The 17th century Dutch poet Voost van den Vondel referred to the fish as "royal herring," not just for the nourishment the fish provided, but for the flourishing international trade it created. Imports of wood for shipping casks and salt for preserving and exports of pickled herring drove a sizeable portion of European trade.
It's a quirk of herring that their migratory patterns are unpredictable; waters that were thick with the fish for decades could suddenly experience dismal catches. According to Time-Life Books' Foods of the World: The Cooking of Scandinavia, "Herring, appearing offshore one year in shoals a half dozen miles long and wide, the next year could vanish almost completely...so varied was the herring that it was looked upon as a bearer of divine messages. Even when herring was abundant, there was always the hazard that there would not be enough available salt to preserve the catch." To eat herring at the New Year was not only a celebratory rite, but a small prayer of sorts, a wish for the catch and the trade to line up with prosperity.
With herring's cultural significance so widely dispersed, the eating of pickled herring for good luck is thus not concentrated in any one region of the United States. However, areas with a large Scandinavian population, such as Norwegian and Swedish communities in Minnesota, will indulge in herring bonanzas this December 31, when tradition dictates to eat the fish at the stroke of midnight.