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Salt went from strategic commodity → taxed necessity → industrial bulk mineral → almost free food additive.

Core timeline

Era	World pop.	Salt production	Price / scarcity status	Breakpoint
Hunter-gatherer	~1–10M	no “industry”	usually not a trade good	Meat/blood supplied more sodium; salt licks mattered locally.
Early farming, 10k–3k BCE	~5–20M	tiny, local	valuable inland	Grain diet lowered sodium intake; inland humans needed salt sources/trade. Census historical estimates put world population around 5–20M by 5000 BCE.
Bronze/Iron Age	~20–100M	salt pans, brine, mines	high-value trade good	Cities, armies, livestock, cheese, fish/meat preservation.
Rome / Classical	~200–300M	organized regional production	important, but not literally gold	Salt routes mattered; “soldiers paid in salt” is mostly myth. Diocletian’s 301 CE price edict gives salt as an ordinary controlled commodity, not a luxury.
Medieval	~250–500M	bigger coastal/brine works	regionally expensive	Transport + monopoly + taxes dominate price.
Early modern Europe	~500–900M	large saltworks	politically explosive	French gabelle made salt artificially expensive; in 1784 a 49 kg unit reportedly cost 31 sous in Brittany but 591–611 sous in heavily taxed regions — ~20× difference.
1800s	~1B → 1.6B	industrial mines/brine	price collapses	Deep mining, drilling, canals/rail, coal-fired boiling, chemical industry. This is when salt becomes broadly cheap.
1900	~1.6B	tens of millions tons/year	bulk commodity	USGS says in 1900 the U.S. was the world’s largest producer at ~23% of world output; major uses were food, animals, leather, fish/meat preservation, with chemical use beginning.
2000	~6.1B	~200M+ tons/year	very cheap	By 2000, food use was only ~3% of U.S. salt consumption; chemical industry dominated.
2025	~8.1B	~270M tons/year	insanely cheap	USGS estimates 2025 world salt production at 270 million metric tons; U.S. rock salt averaged about $54/metric ton, brine about $11/metric ton at mine/plant.

The big inflection points

1.

Farming made salt more necessary

Hunter diets with meat/blood/organs gave more sodium. Grain-heavy diets made salt a thing you had to seek. Inland farming = problem.

2.

Preservation made salt civilization-scale

Before refrigeration, salt meant:

• fish
• meat
• cheese
• pickles/ferments
• hides/leather
• livestock

So it was not just “seasoning.” It was food storage infrastructure.

3.

Governments made it expensive

Salt was perfect for taxation:

• everyone needed it
• hard to substitute
• easy to monopolize
• easy to inspect/impound

France’s gabelle is the canonical example: not “salt is rare,” but the state turned salt into a tollbooth.

4.

Industrial extraction killed the old price

The real “salt becomes cheap” breakpoint is roughly:

late 1700s → late 1800s

Because of:

• rock-salt mining
• brine pumping
• coal-powered evaporation
• canals/railroads
• steam machinery
• later: chlor-alkali chemical demand

After that, salt becomes a bulk industrial mineral, not a precious foodstuff.

So, when was salt “common enough”?

Best rough answer:

• Coastal people: always relatively available, but labor-intensive.
• Inland premodern people: available through trade, but sometimes expensive.
• Urban medieval/early modern Europe: common, but heavily taxed/monopolized.
• By late 1800s: common and cheap in industrializing countries.
• By 1900–1950: basically modern-cheap.
• Today: absurdly cheap; the expensive part is packaging, branding, transport, and grocery markup — not NaCl itself.

One-line model

Salt was never uniformly “worth its weight in gold”; it was cheap at the source, expensive inland, politically exploitable, then crushed by industrial mining and transport.