Hi C.,
I just went thru the same thing with my 16 month old. I used the same book I used with my now 6 year old to get him to fall asleep. The book is called "Helping Your Child Sleep Through The Night" by Joanne Cuthbertson and Susie Schevill. I used it when my 6 year old was 9 months old and it took 2 weeks and he started sleeping thru the night.
Two weeks ago I tried it with my 16 month old and it took him 3 days to sleep through the night. For the most part he sleeps through the night unless he doesn't feel well. There are several methods in the book. But the methods I used were to develop a routine (which you already have) then I held a stuff toy as I held my son so he could associate the toy with comfort. Next, I stopped rocking him and put him to bed while somewhat awake so that he can fall asleep on his own. He still cried but then I followed their advice on waiting 5 minutes to rub his back and softly tell him to go back to sleep, then 10 minutes then 20 minutes, then 30 minutes...After that I would just come in every 30 minutes until he went to sleep.
I will say this, I did not use that strategy with my now 4 year old and he still does not sleep through the night most nights (he wakes up sometimes during the night with issues of more water, monsters, can't go back to sleep, etc.) We were not as firm with him. My hubby and I held him throughout the night everytime he cried thinking he would grow out of it. His 4 and I am still waiting for him to grow out of it. : )