Limestone: The Secret Ingredient

Shallow Seas, Bountiful Bourbon, & Hearty Horses

We know limestone-rich water makes for hardy horses & tasty bourbon in the Bluegrass. How, exactly, has this humble rock altered the course of history?

‘“The water is a very important ingredient and is a key reason why the bourbon industry has flourished in Kentucky,” wrote Susan Reiger in Kentucky Bourbon Country.  “The state’s limestone geology means that iron is filtered out of the water as it flows over the rock and becomes a sweet-tasting mineral water. Whiskey made from water containing iron would turn black, which is absolutely unappealing.”’

In fact, the same thing that makes Kentucky’s limestone filtered water superior for bourbon production is also one of the things that make Thoroughbreds flourish here.  The calcium and other minerals in the water and bluegrass give horses strong bones.” (Makers Mark concurs.)

Additionally, “the gently rolling hills are caused by the weathering of relatively thick-bedded limestone that characterize the Ordovician strata of central Kentucky that has been pushed up along the crest of the Cincinnati Arch” (Kentucky Geological Survey). Those same hills have strengthened yearlings for hundreds of years.

So, what is limestone? How is it formed?

“Limestone is a sedimentary rock composed primarily of calcite, a calcium carbonate mineral…It usually forms in clear, calm, warm, shallow marine waters. Limestone is usually a biological sedimentary rock, forming from the accumulation of shell, coral, algal, fecal, and other organic debris.”  (

So, what is limestone and why does Kentucky have so much of it?

For a good portion of Kentucky’s prehistory, the land was covered by tropical shallow seas. Marine life fossils from this time period helped form the abundant limestone found here. In fact, the state fossil of Kentucky is that of a shelled organism, the brachiopod.

This rich limestone bases imparts needed minerals to Bluegrass water & soil. Crop land is further enhanced by the enriched natural resources. Whereas many farmers elsewhere (including Martha Stewart) lime their fields to reap these benefits, “it is very unusual to need calcium or magnesium fertilizer on Kentucky soils, which typically have plenty of both available for plant growth…” (University of Kentucky Extension Office)

We incorporate soil mapping into our marketing of any farm of size when selling.  Locally-favored types like Maury & McAfee are rich in limestone- perfect for crop land, natural woodlands—and horse farms.

Let’s all raise a glass to the ancient seas of the Bluegrass!

Soil map prepared for farm sold by Kirkpatrick & Co.
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