Since 2001, librarians at Oregon State University's Valley Library have been working to build a "teaching library" supported by a clearly articulated instruction program. From the start, we believed that we needed to assess the teaching library's impact, not only to determine the success or failure of our efforts but also to demonstrate the need for intentional, proactive information literacy instruction on our campus. No single assessment tool or method proved adequate to effectively measure student learning happening both inside and outside the library. We describe our evolving, multi-pronged approach to measuring the impact of the library on student learning in the context of current assessment practices in academic libraries and higher education. (Contains 1 figure.)