Date: Mid- to Late-19th Century (Edo Period)
The history of the denim jacket truly begins with indigo dye. Indigo has been a crucial dye in garment production for centuries, dating back to when the Silk Road was a major trade route, and the dye moved across the globe. In Japan, now known in modern times for its sheer mastery of indigo dye and denim, the origins of the denim jacket were first seen with indigo-dyed garments in the 1800s.
Back then, firemen wore specific chore coats known as Hanten. These ancestors to the modern denim jacket were woven out of wool, as silk and finer fabrics were forbidden by the Tokugawa Shogunate to those in the laboring classes. Indigo dye was used to denote what fire squad an individual belonged to, along with symbols to inspire luck or bravery. Naturally these weren't the best materials to fight fire with, and were constantly doused in water to prevent stray embers from lighting them ablaze while on the job.