The Friday File: The #1 wine producing nation in 2013 was Italy with 1.2 billion gallons (BG). Spain followed with 1.13 BG then France with 1.1 BG. Collectively, these three nations produced 46.8% of all wine. Rounding out the top five was the USA with 581.2 million gallons and Argentina at 396 million. In 2012, California produced 88.5% of US wine; Montana produced the least; just 0.002% of US production.