Wine has historically been a very important part of the Jewish diet. The Torah provides specific instructions for the caring of one's vineyards and the sacrificial requirements of wine. Furthermore, Jewish law has nuanced details about how wine can be produced and the strict regulations over how and when it can be considered kosher (or treyf).
It was very important for Jews in America, as in the rest of the world, to have a reliable source of kosher wine for use during holidays and other festivities. Traditionally, wine was made by individuals in their own homes (as attested by recipes and memoirs), but with the growth of industry and value-added food purveyors, a market for kosher wine was created. Traditionally, these wines were very sweet sacramental wines (like today's Manischewitz and other concord grape wines) and were generally sold exclusively in the Jewish community.
Today, the kosher wine business in America is huge. In addition to the very sweet concord reds, there are scores of kosher bottles that are seemingly indistinguishable from their non-certified counterparts.