Hi hdunlop,
Another legal history person here. Legal history is a growing field, super-interesting, previously under-studied, and with extra employment prospects since law schools are an option. It's a great path to consider.
Some other things to think about:
1. Obviously, the first thing to think about is whether you really need this JD. I would say that depends on how and from what angle you want to study legislation. A simple test to start with: think about the actual law school curriculum. Will learning these subjects in any way help you do research you couldn't do otherwise? You should know that to be admitted to a history department as a JD-PhD student you will have to explain very persuasively why you need both degrees, and what law as a field contributes to your research.
2. If you have decent numbers, law school admission is much, much easier than history. I would not assume that you'll be admitted to the joint degree program if you reapply as a 1L. Have you been in touch with the history department at this school? Have they given you any positive signs that you might be admitted if you reapply next year while already a 1L?
3. Is this really the program where you want to get your legal history degree? How many profs are doing legal history in the law school? (Look for at least 2-3.) Do they have any legal history students right now? (Look for at least 1-3.) How are those legal history students doing on the market? Are there legal history workshops, speaker series, etc.? Do legal history profs at the law school seem to talk with history profs, and are there people with true joint appointments? The reality is that even if you have decent fits in each school individually, it will be harder to do legal history at a place without a strong legal history community with support from both schools. There are not actually too many of those! Make sure this school is one!
4. You mentioned you might transfer, indicating that you might apply more broadly than just the school you're already attending. Are you really prepared to do a full round of applications to both grad schools and law schools while in the midst of 1L? Keep in mind that a) transfer admissions are more competitive for law schools, and your 1L grades are extremely important if you have any interest in being a law prof.
5. How will you feel if you don't get into a grad program as a 1L? Are you prepared to finish law school and reapply for a PhD afterward? This is still the most common way people enter legal history, so it wouldn't be a disaster, in my opinion, but maybe you feel differently. Better to think about this now.
6. So speaking of being a law prof, do you want to teach in a law school or a history department? Before you say "history department" too quickly, think about the fact that the law prof market is significantly less terrible, tenure reqs are easier, and salaries are double. Personally, I think you should keep your options open. If you do want to have the option of law teaching, you should know that going to a T20 law school, as opposed to a T14 or even better a T3, will significantly hurt your chances. Law school hiring is very credential-oriented, significantly worse than history that way. Check out the Leiter Law Reports blog and PrawfsBlawg entry-level hiring report for more info on law school hiring. Seriously, it is scary how many law profs are from the T3. Things are getting better, I think, and having a PhD will help, but still, you should remember the name on your degree matters.
7. Full scholarships to law schools are great. Do not underestimate this. However, some schools have LRAPs that cover academic employment (Yale, Harvard, not sure who else) and this can be almost as good. Also, if you get into both programs at once, many schools will fund your law degree, including schools that do not otherwise give merit scholarships. Also, law profs make enough that having some moderate debt is not as terrible, especially since you have a plan B option (being a lawyer) that's less scary financially than long-term adjuncthood.
8. Law school applications are rolling, and applying late hurts you. If you applied in February as a back-up and got into a T20, you could very likely do better if you reapply earlier in the cycle.
Sorry for the very long post! In conclusion, I would start law school now if and only if all of the following are true:
a) You really and truly want to do legal history, Your law school is about as high-ranking as you can expect to get into based on your numbers, or decently close,*
c) The school does well when you ask the questions in #3 above, and
d) The history department gives you some positive indication about your prospects next year and/or you are comfortable doing JD first, PhD second.
* I would be less strict about the ranking thing if you had already been admitted to the PhD program, because I think some sacrifice in law school ranking is worth it to be able to do the joint degree at an awesome history department rather than do it sequentially. However, you do not have that counter-balancing factor, so there's no reason not to give yourself the best law credential you can get.
Otherwise, reapply next year as an actual joint degree applicant. Get your law school apps in by mid-November, refine your interests for a stronger SOP, have a legal history writing sample or make a strong cases for how legal history methods could extend & enrich your existing work, and all that jazz.
Good luck! Happy to answer more questions, via PM if needed. (Legal history is a very small field.)
Best,
qrsty