The original Levi Strauss work trousers were made from cotton denim.
Denim is a sturdy cotton fabric traditionally woven with a blue warp yarn and a lighter weft yarn. This twill construction gives denim its characteristic diagonal surface texture and helps it withstand heavy wear.
Levi Strauss and Jacob W. Davis used denim for their riveted trousers because it was durable and practical for miners, laborers, and other workers. The copper rivets reinforced points where the cotton fabric was most likely to tear.
People sometimes confuse denim with the indigo dye itself. Indigo creates the familiar blue color, but denim is the woven cotton fabric. Levi’s later products used many fabrics, washes, and blends, while the original workwear was cotton denim.