In the 18th and early 19th centuries, rice was the chameleon crop of the Atlantic world. It could seemingly stretch to fit almost any culinary gap.

The primary use of rice was as a substitute grain-flour, often mixed with wheat or corn for breadmaking. About one third of the rice crop, fluctuating annually by how good the wheat harvests were, was simply sold domestically, in other American colonies. Most of it, however, went to serve the same function in parts of western Europe!

The biggest buyers were the Netherlands and Germany, by far. Portugal and to a lesser extent Italy were smaller but important markets. Portugal in particular was a key purchaser in the winter and spring, as its domestic stores of grain were diminished awaiting their own harvest.

England, despite being the first European port of entry for most American rice, was not actually a profit-rich market itself. Some scholars have suggested England had healthy enough supply lines to flex in times of famine rather than paying the rice import premium. Others have pointed out that England did in fact have wuite a taste for rice--just, as rice pudding, which required milk and somewhat-expensive sugar. So people would be less inclined to see it as a flour substitute, or to buy it when they could not also afford sugar.

Of course, you'll notice two very big western European gaps here:France and Spain. France actually flat-out banned American rice, initially for reasons of rivalry with England. Spain, on the other hand, found it more economic to purchase rice from Turkey in the circum-Mediterranean trade (which France could also tap into).

But one of the main reasons rice was so profitable was that there was an outlet, a dumping ground, for even low quality individual crops or harvest years. White plantation owners in the Caribbean would buy the rejects in bulk to feed their slaves.

But the joke would eventually be on the slavers: rice was so labor-intensive, and unpleasantly so, that the end of slavery was also the end of rice cultivation in the southeast. Production shifted ever further southwest, and relied more on technological developments than a captive, badly treated and badly fed slave labor force.