When businessman and entrepreneur Levi Strauss started out in 1849, he sold dongri to working people. Dungaree - a white canvas fabric named after Dongri in India - was popular among workers in the gold mines during the California gold rush. The fabric was strong and when made into jeans, men could work longer before their pants wore out.
Levi Strauss was an entrepreneur and wanted to make work pants that were better than all other work pants. Then, after putting their heads together with Jacob W. Davis, they patented copper-reinforced seams that made the canvas pants (canvas jeans) more durable at the seams. Strauss also chose to dye his cotton pants with Indigo. The reason is quite simply that this plant has a property that makes cotton stronger.
That, along with the strong cotton treated with indigo, led to the best work pants the gold miners in California had ever had: the iconic Levi's 501. The rest is history and the jeans still have copper reinforcements and are most often dark blue.
It is the indigo plant that gives the yarn its color. All natural fibers can be dyed in indigo, which is also said to have healing effects on the skin.
It is difficult to dye with indigo. Watch the video from Muezart below for a short introduction to the well-known and beloved indigo plant.

