Slice the cucumbers into 1/4 inch thick discs.
Cut the onion in half through the root end, peel, and then thinly slice. Discard the root end and peels of onion.
Combine the cucumbers and onions evenly between 3 quart-sized glass jars with lids. Pack the vegetables tightly into the jars. Use a fourth jar if necessary.
Combine all vinegars and bourbon in a pot over medium-high heat and bring to a light simmer.
Add the maple sugar and salt to the simmering vinegar/bourbon mix and stir until fully dissolved.
Add all remaining spices to the pot and simmer for about 5 minutes to allow spices to release their flavors into the vinegar solution.
Pour the hot vinegar solution directly into the prepared jars and fully cover the cucumbers and onions, ensuring that everything is fully submerged in the liquid.
Place the lids on the jars and allow to cool to room temperature then store in the fridge.