Improving mathematics education in the United States has taken many forms. Our work has focused on two aspects: the content knowledge of teachers and a well-articulated coherent curriculum. Our aim was teacher "capacity building" that is enabling teachers to teach to coherent and significant mathematical curricular goals and describe the implementation in a large-scale project based at Michigan State University. We highlight the design, structure and use of mathematics teacher learning tasks that were intended to improve teachers' capacity to teach to these goals and note how the teachers' perceptions of the structure and sequencing of mathematics itself affect the ways they organize mathematics in their teaching and the ways they teach.