3 Counties Spirit Company

When you examine the text on the back label of the Kirkland Signature Irish Whiskey bottle (available in the United States), you'll discover that the whiskey is imported by MISA Imports, a liquor importing and distribution firm based in Dallas, Texas. This serves as a starting point for further exploration on their website, where they showcase a range of products and trading partners. In the "Whiskey" section, their Irish whiskey selections feature Galtee Mountain Boy, Irish Rover, and Ballykeefe.
Upon investigating these three brands, we find that two of them—Galtee Mountain Boy and Irish Rover—are produced by the same distillery: 3 Counties Spirit Company, located in Thurles, County Tipperary, Ireland. Both whiskeys are triple-distilled and have a minimum aging period of three years in bourbon casks. These characteristics align well with the description on the back label of Kirkland's Irish Whiskey, which notes that it is also triple-distilled and aged for four years.
Interestingly, the distillery's homepage mentions that it collaborates with "a long established network of distributors" to facilitate the journey of its spirits from production to the consumer's glass, which includes MISA Imports. It’s not too far-fetched to consider that Costco and its Kirkland brand might also be part of this distribution network.
Ballykeefe Distillery

The second company highlighted by MISA is Ballykeefe Distillery. A brief search reveals that this distillery is situated in the quaint town of Cuffesgrange, County Kilkenny, Ireland. According to the presentation slides available in MISA's portfolio, Ballykeefe is a family-owned establishment that has garnered numerous accolades and awards over the years for the excellence of its spirits. They offer an extensive range of products, including two private-label Single Malt and Single Pot Still Irish whiskeys. Although these whiskeys do not carry age statements like those from 3 Counties, they are both triple-distilled and matured in oak casks, aligning with the general description of Kirkland's Irish offerings.
The company did not indicate any partnership with Costco (or any partnerships at all), but since it is part of MISA Imports' portfolio, there remains a possibility—albeit slimmer than with 3 Counties—that their spirits could be included in a Kirkland's Irish bottle.
In summary, while both options are plausible, it remains challenging to definitively identify the source of the delightful liquor found in Kirkland Irish whiskey bottles. However, as long as it is affordable, delicious, and readily available, we have no complaints as we enjoy our Irish whiskey-infused iced coffee.
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