One of the first Native American tribes to move from being hunter-gatherers to traders was the Miwok, and now the evidence of that transition has been found.
United States Geological Service researchers James Moore and Michael Diggles have located a site halfway between Yosemite and Tahoe where 369 circular basins were once used to distill salt which was then traded for food and other items by the Miwok. Carved in glaciated granitic bedrock in a canyon on the west slope of the northern Sierra Nevada, the salt-collecting depressions are a meter-and-a-half across – much bigger than those found in the more plentiful acorn grinding rocks, according to Diggles, and nearly one meter deep.
The work done by Moore and Diggles indicates that the basins have been laboriously excavated in granodiorite by Native Americans to contain and evaporate water from a nearby salt spring to produce salt as a commodity. Fires built on the granite makes it flake off very readily. By repeating this operation for some time the collection depressions were made.
“There are hundreds of them, located next to the salt spring,” Diggles said. “There aren’t a lot of salt springs around, and most of those are poor. This salt is good stuff – my wife cooked with it the other day. I carved a bit off the side of a rock with my Swiss Army knife and brought it home. Good salt.”
Two saline streams ran from the spring providing saline water for evaporation in the depressions.
From what he and his colleague saw, Diggles concluded, “They were producing a whole lot more salt than they needed, a ton-and-a-half of salt in a season.”
The main salt-making season is assumed to be 122 days in the warm months of June, July, August and September, Moore and Diggles said in their report. This is the period with the highest temperature, highest sun angles, and greatest evaporation rates, and it is almost free of rain and snow.
Diggles described an account written before the Gold Rush that talks about an encounter with a Washoe Indian who was on his way across the crest of the Sierra to trade for salt. “So, the salt trading was still going on as recently as the early 1800s.
“We don’t know what the oldest age might be,” he said, referring to the salt collection depressions. “They could be as old as 8,000 years. They don’t wear out. They’re not like the acorn pounding stones that get deeper with use.
“Fire was probably used to heat the rock, reducing its strength and making it easier to grind. To deepen the basins just one centimeter, they had to build and maintain a hot fire on the rock, let it burn out, and then pound the bedrock with stone tools.” The Miwok had to repeat the process 100 times to carve a three-foot-deep basin. Diggles estimates it would have taken several workers nearly a year to make one basin.
“It’s not that hard, you just build a fire and let it burn out. You spend a lot of your time just gathering firewood. A lot of firewood.”
Ten families could have harvested the salt from the 300 plus basins, Diggles estimates. “But, those people wouldn’t have time to do anything else.” He estimates it took a minimum of 40 Miwok families to support the salt makers.
“The site is the most impressive prehistoric saltworks yet discovered in North America,” Diggles and Moore said in their report, “and represents a unique departure from traditional hunter-gatherer activities to that of manufacturing.”
The grinding of so many basins in granite could not have been done without the labor of a concentrated population.
In about the same area, Paiutes guarded their salt gathering sites and kept many areas secret from other tribes. There were old tales of skirmishes with other tribal groups over the salt “mines” and springs the Paiutes guarded vigorously.
Miwok coastal Indians gathered salt where natural honeycombs in the sandstone would catch ocean salt spray and allow it to dry in pools. Visited just once a year, the salt gathering locations were jealously guarded by the tribe from salt poachers. This precious resource was eventually replaced when Europeans used firewood and kettles to accomplish the same thing more quickly.
The site of the Sierra Nevada salt basins is on land administered by the U.S. Forest Service. Because of the site’s archaeologically sensitive nature, the exact location details have not been made public.