The Upper Loire Valley is the smallest region, yet home to it’s most famous and exported appellations: Sancerre and Pouilly-Fumé. The region was under the influence of the Duchy of Burgundy for most of its history - and was once heavily dominated by Pinot noir. In the 19th Century, Phylloxera decimated many of the Pinot noir vineyards which were then replaced with the easier to cultivate Sauvignon Blanc. Cementing it’s reputation on the variety for a fresh, flinty, crisp white.
Sitting on the right bank of the river, Sauvignon Blanc is the only sanctioned grape and the region owes its name to the “smoky” attributes wines have from being grown on silex - Flint soils sitting on Kimmeridgian Limestone. Forming the greater appellation is Pouilly-sur-Loire, which is primarily made with the Chasselas grape, seen less and less and more often blended with Sauvignon Blanc these days.