This paper reports on the development of a Learning Pathway for Number (LPN) with the aim of facilitating the teaching and learning of whole number in the early primary grades (Grades R-4) within the South African educational context. The development of the LPN was based on the Dutch Learning/Teaching Trajectory for Whole Number (Van den Heuvel-Panhuizen, 2001). This paper describes a case study that presents the development of the LPN with three teacher groups (teachers from a school improvement project, teachers from high-performing schools and pre-service student teachers). The LPN is a conceptual framework based on five learning/teaching principles, namely the context, level, activity, interaction and the guidance principles. The benefit of this pedagogic tool adapted and refined for the South African context is that it provides a longitudinal view, highlighting milestones in the learning of number with the aim of deepening learners' conceptual understanding of number over time. This case study reveals the importance of a device that enables teachers to reflect on their mathematics content and pedagogy and bridges the theory-practice divide. It also highlights the critical issue of language and the use of appropriate terminology and activities in the classroom.