The Selection Committee is looking for the most promising young scholars in the social sciences (including history and law). Your research proposal should make a compelling case that the Selection Committee should select you above the other 700 applicants.
Your research proposal should be no longer than 2500 words. The Selection Committee is most interested in the relevance of your research to your discipline and the contribution your research makes to your discipline. These should be clear in the research proposal.
The Selection Committee is also interested in how you intend to use the two years of the fellowship. In many cases, Academy Scholars intend to use the first year to prepare the dissertation for publication as a book or a series of articles and the second year for a new research project. If applicable, scholars should summarize their publication plans and future research plans. If you expect to begin a new research project in the second year, you should introduce the topic and perhaps explain how your new research continues/expands your doctoral research or takes you in a different direction.
Applicants may wish to consult the essay "On the Art of Writing Proposals" (PDF) by Przeworski and Salomon on the SSRC website. Note, however, that this essay is written with specific proposals in mind, rather than The Harvard Academy's broader interest in an applicant's research and her or his plans beyond the first project.