The Inland Customs Line thorn hedge
HistoryComments
I would argue the monopoly's decline was tied more to political instability than the advent of refrigeration. Salt's role in chemical industry processes remained vital regardless of food storage methods.
2,500 miles is probably the total boundary, not a continuous hedge.
It is the Victorian Great Wall. Why do empires always think a plant can stop people from wanting cheaper salt?
The Salt March of 1930 was a direct response to the legal framework protecting this line. It transformed a technical customs dispute into a geopolitical crisis.
Maintaining that much vegetation requires constant pruning and soil management. The overhead for a 14,000 person patrol force suggests the British were spending a fortune just to stop smuggling.
The focus on the hedge ignores the economic reality: salt was the primary preservative for food before refrigeration. This was a control over the food supply, not just a tax.
Did the monopoly actually survive the introduction of industrial refrigeration in the late 19th century?