This study examined the initial learning trajectories of 13 upper elementary teachers as they developed technological, pedagogical, and content knowledge during a 7-month professional development program to integrate technology into classroom practice. The program was collaborative and non-prescriptive; teachers worked on self-chosen summer projects with flexible support from a university-based partner. A descriptive multicase study tracked teachers' learning progressions through interviews, surveys, digital artifacts, and researchers' notes and memos and found that teachers developed varying degrees of TPACK. Analyses distilled six initial TPACK learning trajectories.