The indigo-dyed item most recognizable today may be the sturdy riveted garment that was born in the bustling mining towns of the West.

Dyed indigo blue and guaranteed not to rip, the premier product of Levi Strauss and Co. - Levi 501s - has become an American classic.The brainchild of a mining-camp tailor named Jaboc Davis, the original Levis were pants of heavy white duck, riveted at the pockets to prevent tearing. Unable to afford a patent application, Davis sold Levi Strauss and his partners limited rights to produce and sell the riveted pants, in return for the patent fee.

On June 5, 1873, Levi Strauss and Co. sold their first pair of the riveted garment in their San Francisco dry-goods store. Two weeks later, they sold the first indigo-dyed cotton denim version of the product. The "waist-high overalls" were known as Double X blue denim 501s. The number was their lot designation; the double X implied strength.

For decades the preferred pant of miners, cowboys and other laborers, and eventually of college students and some movie stars, the heavy-weight denim pants were guaranteed to shrink to fit and not to rip. Their copper rivets, orange thread, stitched pocket design and denim blue have come to symbolize the American West throughout the world.

Levis owe their status as much to the quirks of indigo as to their legendary strength. The blue colorant adheres to the outsides of the cotton fibers, and with extended wear, the color eventually rubs away. As a result, denim woven from indigo-dyed yarns gradually shades from its original dark blue to nearly white.