Quebec City. That's the bit I had wrong all week until I looked it up — I'd always assumed the FAO came out of Rome, because that's where it sits now, but the founding conference was in Quebec in the autumn of 1945, forty-odd delegations, flags along the wall. There's a photo from the hall: a man in a suit at a big microphone, two people watching from the front table with papers and a water jug, and most of the chairs behind him empty.
What they signed up to was mostly counting. How much wheat, how much rice, how many people, where. Paperwork, yes, and a recipe is paperwork too right up until the morning you need to know whether there's flour for the week. Anyway, once somebody's counting the harvest you can see a shortfall before the sack of grain is already sitting in the wrong port. That's why the day lands on the 16th.
The counting turned up something that still surprises people: somewhere around a dozen plant species cover most of the calories humans eat, with rice, wheat and maize doing the bulk of it. Thousands of edible plants out there and we keep going back to three.
Forty-two nations signed in a Quebec hotel, as it happens, with the war barely over and delegations arriving by whatever transport they could get. The first task they agreed on was exactly what you say: count what the world grows, then count who needs it.