This paper describes a thirteen-month, Lesson Study-type professional development project that sought to form and support a community of in-service social studies teachers who could design and implement lessons informed by second-order historical domain knowledge. Here, the researcher reports on the experiences of a subgroup of participants, three secondary history teachers, as they planned, taught, revised, and re-taught a collaborative research lesson. The teachers increasingly incorporated second-order historical domain knowledge into their respective practice: facilitating students’ use of historical photographs as (...) evidence to begin to answer a compelling question. Findings also suggest the teachers began to effectively support students’ abilities to make claims about the past. Implications include: the foregrounding of compelling questions during planning, and the need for explicit guidance to help teachers analyze student work products. (shrink)