The former limestone mine northwest of Louisville, known as Marengo Underground Warehouse, with around four million square feet of excavated space, has been converted into storage and other industrial purposes. It was mined until 1986, when the government leased it to store grain. After that, its owners began developing more of it for commercial use. 600,000 square feet was developed by 2002. In 2012, the Defense Logistics Agency leased part of the cavern for storage, including 10 million MREs (Meals Ready to Eat). By 2013 around 1.3 million square feet was used by 12 warehouse spaces inside. Bridgestone Tires is one of the tenants, using the mine to store hundreds of thousands of tires, as the even temperatures and humidity help preserve rubber. A plant genetics company called Controlled Pharming Ventures has used the isolation inside the cave to develop systems for growing genetically modified corn and tomatoes.