Was Gimli the last of his race?
In the Lord of the Rings and The Hobbit, dwarves play a fairly central role: They drive the entire plot of The Hobbit, and much of Fellowship is centered upon Moria, the dwarven stronghold.
We see scattered references to dwarven kingdoms still existing, yet nowhere in the trilogy does anyone consider calling upon the dwarves for aid.
In the movie, Gimli is seen first with 2-3 other dwarves at the council of Elrond, who are not referenced again (at least in the movies).
He fully expects to find his cousin and other kin alive and well at Moria, even though they've been dead for quite some time (it takes a LONG time to decompose to purely skeletal remains, especially when you're locked away in a mine with a constant temperature and no elements to contend with). This indicates that communication between dwarven kingdoms is infrequent, months or perhaps years without news is not unexpected.
Gathering this all together, then:
- Lots of dwarves die in the trilogy and the prequel.
- No one even discusses calling upon the dwarves for aid against Sauron.
- The dwarves don't communicate with each other frequently.
- Gimli is seen to NOT return to his people after the trilogy.
This indicates to me that Gimli is, if not the last, one of a very small number of remaining dwarves.
Did Tolkien ever discuss this?
just an aside, but when Frodo escapes from Boromir, climbs to higher elevation, and then sits upon the ancient Seat of Seeing or whatever, he looks in every direction and sees that the entire realm is at war. He even looks northward and sees that the Beornings (bear folk), the men of Dale, and everyone is else is at war up there. I think that explains why we don't see men of Dale, northern dwarves, beornings, etc. involved in the wars at Gondor and at the Black Gate---they're involved in a completely different front.
@KorvinStarmast - Please remember that the books are extremely dense and full of a LOT of miscellaneous information that isn't relevant to the plot (and thus is easily forgotten a few years after reading). Plus, this site is not just designed for purists who have read every bit of the source material for their fandoms. Also, there's a fair number of people who have only seen the movies, not read the books.
No, very definitely not.
There are tons of dwarves, all over the place. Gimli's own people [*] mainly lived around Erebor, where they moved to after the events of The Hobbit - Balin's expedition to Moria involved just a tiny group of those, not the whole population. As to why they weren't asked for help during LoTR, Gandalf refers (in Appendix A, section III) to the battles that they fought - against separate armies out of Mordor - while the main action was going on:
Even as Gandalf said afterwards to Frodo and Gimli, when they dwelt together for a time in Minas Tirith. Not long before news had come to Gondor of events far away.
'I grieved at the fall of Thorin,' said Gandalf; 'and now we hear that Dáin has fallen, fighting in Dale again, even while we fought here. I should call that a heavy loss, if it was not a wonder rather that in his great age he could still wield his axe as mightily as they say that he did, standing over the body of King Brand before the Gate of Erebor until the darkness fell.'
But there's nothing in that passage to indicate that the dwarves were wiped out by that battle - and, indeed, the chart on the next page showing the line of the kings of Durin's Folk continues well into the Fourth Age.
Finally, the same section also talks about how Gimli later brought some fellow dwarves to live in the Glittering Caves of Aglarond, the caverns guarded by the Hornburg in Rohan.
[*] who are those descended from Durin, just one of the seven Fathers of the Dwarves.
Further reading on Glittering Caves and Gimli: http://lotr.wikia.com/wiki/Glittering_Caves#War_of_the_Ring_and_afterwards