From the last paragraph on the page 2 article on the slave trade:
“The United States have risen from the rank of a remote and struggling colony into that of a first class Power”.
It’s interesting that they use the plural verb with the United States - in our lifetime, that sentence would start “The United States *has* risen . . .”
On the one hand, it could just be a residual ‘Britishism”. On the other hand the usage given does tend to emphasize some degree of sovereignty of the individual states, while our modern grammatical treatment puts the emphasis squarely on the federal union as an individual entity.
I just wonder how many years after war it was until that change in the grammatical standard took place.
In the Ken Burns Civil War documentary Shelby Foote makes that exact point. Antebellum it was the “United States are.” the war changed it to “the United States is.”