Any information about precolumbian North-American salt trade is welcome. Although I'm particularly curious about how native groups deep within the canadian shield and far from the coasts would get their salt without direct access to evaporites, let alone sedimentary rocks.
Eduardo Williams has written several articles on salt production and trade within Mesoamerica, primarily within Western Mexico. I highly recommend reading his articles and perhaps tracking down any of his sources that catch your interest.
https://www.academia.edu/3821298/Ethnoarchaeology-Salt-Production-Lake_Cuitzeo_Michoacan-Mexico_1999_
https://www.academia.edu/3821165/Ethnohistory_of_Salt_Production_in_Mesoamerica_2010_
https://www.academia.edu/3821156/Ethnoarchaeology_Salt_Production_Michoacan_Coast_2002_
The history of salt in eastern North America is a fairly complicated topic, with salt being in high demand by some nations and reviled by others, with some cultures changing their opinion on the matter over time.
Trade in salt may go back to the Hopewell era (roughly between 100 BCE and 400 CE). The McKittrick Earthworks were built by the Scioto Hopewell at this time, very close (less than half a mile) to spring of Salt Creek in Ohio, which were used by Native peoples to acquire salt into the historic period. We don't know if the Hopewell used salt for their food, though it is likely; what we do know is that they used it in their art, adding a patina to their copper.
The salt trade in the east really takes off among the Mississippians. The Cahokia-affiliated Collins site in eastern Illinois (near Danville, IL) is also situated near a salt spring used historically to produce salt. The Kincaid site (near Brookport, IL), situated on the Illinois side of the Ohio River, near the mouths of the Cumberland and Tennessee Rivers (giving it a powerful position in controlling trade coming out of the southern Appalachians) seems to have received its salt from the Great Salt Springs to the northeast (near Equalty, IL), as did Angel (near Evansville, IN), both of which were the two largest Mississippian polities on the Ohio River. Given that Cahokia relied heavily on the chert trade coming out of the vicinity of Kincaid, it likely received some of its salt from here as well, among other points further south. During this era, we see the widespread adoption and use of saltpans, used to evaporate salt from spring water, among the Mississippians of the Middle Mississippi valley and the Lower Ohio valley (downriver of the Falls of the Ohio), and a bit later among the Fort Ancient cultures above the Falls of the Ohio.
When de Soto and his men were in northern Arkansas, among later Mississippian nations, they encountered a group of salt traders coming down from the north. These men said they got their salt from a mountain range forty leagues to the north (probably the St. Francois Mountains in southeastern Missouri) and offered to take the Spanish there. De Soto sent two men to accompany the traders, and eleven days later they returned with rock salt and copper (another product of the mountains that the traders bartered with in their travels). Not long after, the entrada marched to the town of Calpista (now Bald Knob, AR), which also traded in salt from its local salt spring. Shortly after that, they came upon another salt-producing community, Cayas, situated along Point Remove Creek. The people of Cayas produced their salt a different way. First, they filled conical baskets with the salt-encrusted sand that lined the stream bank. Next, they poured water through the baskets and collected the resulting brine. The brine was strained to remove any residual sand before the water was finally evaporated off in saltpans. The Spanish came across a few other salt-producing communities, but after re-stocking their own supply at Cayas they didn't pay as much attention to the others. The salt produced in this region would remain important in the post-Columbian as well; it was the main supply of salt for the Natchez in southern Mississippi for example and one of the main trade items the people of the Arkansas River offered to the French in exchange for firearms.
Along the east coast and into parts of the Appalachians, salt was generally shunned - greatly disappointing European dinner guests. In the mid-1600s, French missionaries briefly gained access to the heart of the Haudenosaunee - the town of Onondaga, where the Grand Council convene. Nearby they found a salt spring (which would go on to fuel the salt industry of Syracuse, New York), though the people of Onondaga did not utilize it like their Mississippian counterparts. The missionaries recorded the Onondaga opinion of the spring, saying that it was poisonous and associated with an evil spirit. This is probably a misinterpretation of Iroquoian spirituality. Until they largely converted to Christianity, Iroquoian peoples, at least those in the north like the Haudenosaunee and the Wendat (Huron), observed a salt taboo because salt was perceived as inhibiting one's own spiritual power and purity. This taboo can also be seen in other societies to varying degrees. The prophet Tenskwatawa (Tecumseh's brother) refused salt for this reason, and leading up to certain ceremonies Yuchi traditionalists continue to observe the salt restriction on their diet. This, of course, didn't stop Native peoples on the east coast from selling salt to Europeans though, once they found out there was a market for it. Once they fell under the influence of the Haudenosaunee in the late 1600s, Lenape (Delaware) served as middlemen in the salt trade between the salt springs at Onondaga and European markets in Pennsylvania and New Jersey. Those in Albany and New York City got there salt more directly.
The salt taboo casts an interesting light on the Lenape name for Europeans: Schwannack, Salt Beings. It's a word with multiple layers of meaning. Europeans are Salt Beings because they came across the saltwater ocean. They're Salt Beings because they're white. They're Salt Beings because they eat salt. They're Salt Beings because they leave a bitter taste in your mouth. They're Salt Beings because they're cut off from traditional spiritual power.
Sources
Case, Daniel Troy and Christopher Carr. The Scioto Hopewell and Their Neighbors: Bioarchaeological Documentation and Cultural Understanding
Emerson, Thomas E. and R. Barry Lewis, eds. Cahokia and the Hinterlands: Middle Mississippian Cultures of the Midwest
Hudson, Charles. Knights of Spain, Warriors of the Sun: Hernando de Soto and the South's Ancient Chiefdoms
Lewis, R. Barry. Kentucky Archaeology
Mann, Barbara Alice. Iroquoian Women: The Gantowisas
Muller, Jon. Mississippian Specialization and Salt
Baugh, Timothy G. and Jonathon E. Ericso. Prehistoric Exchange Systems in North America (I didn't actually use it here because I don't currently have access to a copy, but you should look into it if you can).