system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why was salt so valuable in the past?

Why was salt so valuable in the past if people already knew that salt came from the ocean and could be extracted via evaporating sea water?
gpt
There's not a lot of real estate that's suitable for extracting salt from seawater with ancient methods.  You need clay soil (so the sea water doesn't seep out of your evaporation pond).  You need a long dry season (so the rain doesn't keep filling up your evaporation pond), ideally with a lot of wind.  You need to be on the coast, so you can get seawater.