The history behind "St. James, starting with "Buck's Elegy" and "The Unfortunate Rake" has been discussed exhaustively in Mudcat threads, 3918 a good place to start. North American progeny are widespread: all wrapped

I very much doubt that the many versions known in North America stemmed from the "hillbilly version" collected by Sharp, since versions of the song were widespread in North America, about soldiers, sailors, lumbermen, stockmen and cowboys, miners, gamblers, drivers, a murder victim, 'bad girls,' etc. It was played at the funeral of "Miss Flora" by the Stockman's Band in Dodge City (1880s).
(Miss Flora was a hound dog, a 'bystander' shot in a gunfight)

"Careless Love" is basically a song from the British Isles, but most of the verses now sung are floaters, many from Afro-American sources. Its popularity largely stems from sheet music pub. by Pace & Handy Music in 1921, probably written by Handy, called "Loveless Love" or "Careless LoveBlues." Some versions can scarcely be related to the antecedent(s), one of which probably is Thomas Moore's "To Sigh, Yet Feel No Pain," written about 1800.

1st verse:
To sigh, yet feel no pain,
To weep, yet scarce know why;
To sport an hour with beauty's chain,
Then throw it idly by.
To kneel at many a shrine,
Yet lay the heart on none;
To think all other charms divine,
But those we just have won;
This is love, careless love
Such as kindleth hearts that rove.

From "The Blue Stocking;" appeared in the John Beach MS, 1801, Gloucester, MA.

A 19th c. songwriter (pub. in Baltimore; in Levy Sheet Music) changed the chorus to:

This is careless, careless love,
Such as kindleth hearts that rove.