Over the past several years, sourcing has become a hot-button topic in the whiskey community. While the days of outright obfuscation may be behind us (even holdouts like Templeton Rye and WhistlePig finally came mostly clean about the source of their spirits), sourcing remains a topic that tends to make even the most polished marketing teams go mealymouthed.

Midwest Grain Products, one of the nation’s largest suppliers of whiskey and other spirits to non-distiller producers, is famously cagey about some of the specifics of its business. MGP spirits are thought to be in over 100 different whiskey brands, and…