Interstate batteries are manufactured by Johnson Controls, which is probably the largest private label supplier in the country.
Johnson Controls also manufactures Costco's Kirkland batteries, Autozone's Duralast, Sears Diehard & Wal-Mart. Johnson Controls also have their own brands too. Optima, Varta, Heliar, list goes on.
http://www.themanufacturer.com/us/pr...hnson_Controls
Sams Club AGM's are now manufactured by exide Deka (east penn) Company