I’ve always imagined that the customs operations were carried out mostly at the actual points of entry, i.e. on the immediate premises of the airports and harbors involved. So I’m curious about these laege buildngs they maintained some blocks away from the harbors. What do they use all that floor space for? Offices? Warehousing contraband until it can be destroyed, or the duty paid?
Part of it was for representative purposes. In the pre-income tax time, customs duties were the major source of revenue for the federal government, so the customs service was an important government department, and it’s inspectors were powerful people in the ports they were in charge of.
Bureacracy. Customs duties are basically a tax, and there was a massive amount of paperwork associated with customs - declarations and returns submitted by those importing goods, applications to lodge goods in bond (and so defer the payment of customs duties); applications to re-export goods (and so recover customs duties already paid), etc, etc. And these would all have to be processed, checked, audited, responded to, etc, etc, and there would be a cash office where money was paid in and paid out, and an accounts department to keep track of that. Physical inspections on the quayside or in warehouses were mainly to ensure that the physical goods corresponded to what had been declared in the paperwork submitted, but most of the actual work was done away from the port, at the custom house.
Plus, the custom house might well accommodate other agencies of the federal government - no need to establish separate premises for every federal agency that might have business to transact in the city.