The Gemara describes many Halachos that apply when someone gets married at very young ages, many under 12, and even a few for the age of 3. There are stories of people who did get married at such ages (Rivkah, ATSO1). I've heard that during the times of the "Cantonists" some parents had their children married at extremely young ages so that they wouldn't be drafted.
Was it ever common for people to get married at very young ages? If so, was it the norm? When?
(Assume here that "young" is 13 and under, although if it was common to get married at, say 15, I'd like to hear that too.)
I have intentionally made no distinction between boys and girls. Include them both.
1According To Some Opinions.