The current decade is likely to witness an unprecedented focus on mathematics curriculum in the U.S. The adoption of the Common Core State Standards for Mathematics (CCSSM) by all but a few states represents a major change in curriculum governance. For the first time ever in the U.S., a large majority of schools, teachers and students will focus on common, specific and grade-level focused learning goals for mathematics. Coupled with mandated common annual grade-level assessments aligned to CCSSM, this initiative is likely to impact other important systems and factors critical to student learning including instruction, curriculum materials, teacher training, and course-taking/graduation policies. This paper provides a summary of current curriculum reform initiatives in the U.S. We provide a brief overview of the current movement toward common (national) curriculum standards in the U.S. We examine some of the procedures used in developing textbooks and discuss some of the challenges textbook authors and publishers face. We reflect on the critical role that mathematics textbooks play in determining the mathematics content students have an opportunity to learn. Finally, we speculate about the future of curriculum materials and the impact of CCSS on school mathematics programs.