Writing across the curriculum (WAC) programs had their genesis in grass-roots efforts to promote attention to writing in all disciplinary areas. At first based on generic faculty-development activities with little regard to systemic and institutional concerns, WAC programs are now more often engaged in assessment and research of writing, especially to measure the effects of the program on student learning and development. Yet little scholarship in WAC has analyzed assessment efforts in light of locations and types of WAC activities. This essay first describes two axes, one representing the "space" or location of WAC activity, and the other representing levels of assessment and other research on writing. When brought together, these axes create a matrix of possible types and centers of WAC activity. A case is made for the "department" or "academic program" as a locus of activity for WAC implementation and assessment that has not been fully explored in program development. (Contains 4 figures.)