Some of the "folk" explanations I read of this variation were quite intriguing. (Most come from here).
One was quite refreshing in its consideration of phonological factors, but was unfortunately sort of crazy: "Perhaps, the British use an 's' ... because they pronouce [sic] the word with the accent on the second syllable (toWARDS). S makes an easier transition to the following word; whereas Americans say "TOward" and it flows more easily to the following word so that the 's' is unnecessary."
The British do use a linking r (as in the famous "lore-and-order" pronunciation of law and order), but no linking s that I'm aware of.
Some felt that toward was used with singular subjects and towards with plural subjects (e.g., He walked toward the water's edge vs. They walked towards the water's edge.) Others advocated the opposite (by analogy with third-person present verbal forms). Somewhat ominously, one person said they had been taught one or other of these theories in school and that their teacher had seemed very convincing.
An interesting comment was that towards sounded "backwoodsy." (Perhaps because the -s isn't perceived to be performing a function and therefore seems archaic or obsolete?)
This rant I found rather less interesting because it was so ill-tempered, but it does give the lie to the notion that towards is exclusively British:
I am sensitive about the distinction between
toward and towards because of an incident
involving the proofs of a book of mine being
published by Cambridge University Press in New
York. The copy editor, who seemed to be under
the impression that he/she had a better ear for the
English language than I do, consistently changed
my "towards" to "toward." Seemingly, the copy
editor took the s-less form to be more American-
sounding, but since I'm American I feel entitled to
make up my own mind (though I have to admit
that my mother is English, so maybe I picked up
the habit from her.) Anyway, I just strew "STET"
all over the manuscript to leave my version alone.
I am sensitive about the distinction between
toward and towards because of an incident
involving the proofs of a book of mine being
published by Cambridge University Press in New
York. The copy editor, who seemed to be under
the impression that he/she had a better ear for the
English language than I do, consistently changed
my "towards" to "toward." Seemingly, the copy
editor took the s-less form to be more American-
sounding, but since I'm American I feel entitled to
make up my own mind (though I have to admit
that my mother is English, so maybe I picked up
the habit from her.) Anyway, I just strew "STET"
all over the manuscript to leave my version alone.
Quite apart from the fact that the past tense of strew is strewed, this author also overlooks the possibility that the copy editor was following house style. All good editors do, even when they disagree with the style on specific points.
It all seems to boil down to the fact that most English speakers have lost a sense for how the -s is functioning in towards, and for that matter also in backwards, sideways, once, and widdershins.
I'll write about that in my next post.
I'll write about that in my next post.