a) History

iii) Industry According to historic documentation on the Shirakawa-go / Gokayama area, because of the mountainous terrain and the scarcity of flatland, rice-field agriculture had very limited success, and to supplement the inadequate rice yield the farmers had to turn to production of minor grains such as buckwheat (soba) and millet (awa and hie), cultivated in small fields. Even with these crops, agricultural production could not exceed the level of subsistence farming. In addition to the shortage of agricultural capacity, the surrounding forests and mountains also offered a poor yield -- with only limited food products (such as nuts, mushrooms, and other edible wild plants), firewood, and derivative products such as charcoal, wax and lacquer. The few marketable products of this area which could help compensate for the poor agricultural conditions included Japanese paper (washi), material for gunpowder production (ensho, or calcium nitrate), and the basic products of sericulture (the raising of silkworms and the production of raw silk thread). Japanese paper is made from the fiber of the paper mulberry plant (kozo) which grows naturally in this area. Although paper making is very time-consuming and requires intensive effort during the production process -- from the harvesting, the peeling of the skin and the bleaching work to the final step of producing the paper sheets -- it is an ideal income-producing industry for a mountain village which has no agricultural products for sale, where the long snow-bound winter months can be put to good use for indoor work. Although it is not known exactly when hand-made paper production began in this area, there is written material from the beginning of the Edo Period which documents that the production was already under way at that time. Paper production continued all through the Edo Period but naturally declined after the introduction of western paper making processes from Europe in the beginning of the Meiji Period (mid-19th century). The production of ensho, the calcium nitrate material used to produce gunpowder, was strictly controlled and specially protected by the authorities of each area because of its importance to the military. The production of ensho in the Shirakawa-go / Gokayama area involved mixing various grass-like plants (including mugwort and other varieties) with cattle manure, human waste and ordinary soil, then allowing this mixture to decompose for three or four years, after which the calcium nitrate was extracted by a refining process. The production of ensho in this area started around the middle of the 17th century and continued throughout the Edo Period, but in the Meiji Period, after the importation of cheap saltpeter from Europe, government procurement of ensho from this region was stopped and production disappeared altogether. Ensho production required extensive labor to harvest the necessary large quantities of grass. The refining and extraction processing work was done indoors during the winter period, which meant that this type of industry, as with paper production, was also ideally suited as an income-producing side occupation for these mountain village residents. In this area, because the soil-mix decomposition processing was done in deep holes dug under the floor of the house -- in order to keep the production secret -- it was an advantage to have a house with a large floor area. It is assumed that this is one of the principal reasons why these houses were built on such a large scale, with an unusually large proportion of the floor space given to the raised floor area rather than to the earthen-floored space. Records of silkworm raising and silk thread production in this area have been found in early 16th century documents, but sericulture did not become a full-fledged side industry until the end of the 17th century. Stable production continued all through the Edo Period, but corresponding to the increase in the export of raw silk and silk fabrics due to the expansion of foreign trade at the end of the Edo Period, the local sericulture industry expanded rapidly and became this area's most important industry. This industry more than compensated for the decline of paper production and ensho production in the Meiji Period. The silk industry thrived until the 1970s, with a temporary decline during World War II, but due to the permanent decline that began in the 70s the industry has now disappeared entirely. Silkworm production involves labor-intensive work such as collecting large quantities of leaves of the kuwa plant (another type of mulberry) as well as raising and tending to the silkworms themselves. Silk raising in a climate such as this requires a large interior space for the silkworm beds and for storage of the mulberry leaves. These requirements led to the development of the multi-story Gassho-style houses, with the large interior space inside the roof structure divided into multiple levels to increase the usable floor area.