Abstract While the vast majority of existing work on automated essay scoring has focused on holistic scoring, researchers have recently begun work on scoring specific dimensions of essay quality. Nevertheless, progress in dimensionspecific essay scoring research is hindered in part by the lack of annotated corpora. To facilitate advances in this area of research, we design a rubric for scoring an important, yet unexplored dimension of persuasive essay quality, thesis strength, and annotate a corpus of essays with thesis strength scores. We additionally identify the attributes that could impact thesis strength and annotate the essays with the values of these attributes, which, when predicted by computational models, could provide feedback to students on why her essay receives a particular thesis strength score.