Jack Daniel's makes its whiskey in Lynchburg, Tennessee and the process can take up to 12 years. It all begins with yellow corn kernels that are dumped into a mill and hammered into a mash. Then they're mixed with a secret ingredient: cave water! The iron-free water allows the whiskey to ferment. Maple wood is then doused with whiskey and set on fire to be used as ash to filter the new batch.