I assume that historians generally don't get their first publications as undergraduates. Of the later career stages, what is most common for publication?
We are being told right now that 2 published articles during grad school is minimum for serious consideration for an academic job in history. Time to publication being what it is, people seem to get their second one out during a postdoc year in my program. My friends in English are being told 4-5 articles and a book prospectus (proposal) accepted.
The twist, of course, is that quality of journal also matters. So just submitting your seminar paper with a few extra paragraphs to an online grad student journal, not really going to cut it on the academic job market.