The starting point isn't Lloyds or the U.S. Bureaus of Commerce/Shipping; it's a 200 year old bit of pop entertainment not unlike the song itself. Stitch counting historical accuracy was never on offer.

Speculation (imagination) is part of the fun for some listeners. It's a sure-fire fun killer for some others. A lot artists will struggle to recall exactly what they were thinking line-by-line if they haven't looked at them in 40-50 years.

The whiskey's in the jug, boys, the wheat is in the sack.
We'll trade 'em down to Shawneetown and we'll bring the rock salt back.

Today that's 240 river miles, one-way, from Shawneetown to Louisville. 380 miles to Cincinnati. One could do the shorter round trip more than once per month… in season… weather permitting… &c &c. A keelboat is the most often mentioned type but a large canoe, dugout, pirogue or periagua &c&c would not raise an eyebrow. The 1820s 'original' is already lamenting the advent of steam on that stretch of the river.

Alas the pedant, the Ohio River salt trade was an evaporation process (brine)... a fine paste, brittle as chalk or sandstone when dry, but not commercial “rock salt.”


I got a wife in Louisville and one in New Orleans,
And when I get to Shawneetown gonna see my Indian Queen.

Your show-biz trope alarm should be gonging. A girl in every port & debauching the natives has been pop entertainment sailor stock-in-trade since Odysseus & Calypso.