NEW YORK CITY IS the most important wine market in the country, and possibly the world. Not because of its great wealth, its restaurants and wine shops, or even its corps of fast-talking, fast-moving sommeliers, but because the city is home to more influential wine distributors and importers than anywhere else. These are the companies that inform the palates and shape the preferences of wine drinkers everywhere.

There are 219 wine wholesalers in New York City—and their numbers are growing, especially when it comes to small...