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Before refrigeration, salt was among the most valuable commodities traded, since it alone allowed meat and fish to be preserved for months. Early producers relied on solar evaporation in shallow coastal pans, a method still used in parts of France and Portugal, where seawater is channelled through successive basins until only crystallised salt remains. Inland societies without coastal access instead built brine wells, pumping saline groundwater to the surface and boiling it down in iron pans, a far more fuel-intensive process. This difference in method shaped trade routes: coastal salt was cheap and exported widely, while inland salt commanded higher prices locally due to the wood or coal needed to fuel evaporation. Some historians argue that access to efficient salt production was as decisive to a region's early economic development as access to fertile farmland.