The *Common Core State Standards for Mathematics* (*CCSSM*) defines “*what students should understand and be able to do in their study of mathematics*” (*CCSSM*, page 4). *Math Trailblazers* 4th Edition aligns with and incorporates all of the Common Core Standards for Mathematical Content and Mathematical Practice while staying true to the *Math Trailblazers’* philosophy of providing rich, meaningful contexts for students to develop mathematical understanding, strategies, and number sense. Key shifts called for by the Common Core are a greater focus on fewer topics, better coherence that links topics and thinking across grades, and more rigor, requiring that teachers pursue conceptual understanding, procedural skills and fluency, and application with equal intensity. With this and current research in mind, *Math Trailblazers* underwent a thorough revision in both content and structure to reflect the findings of our research and to accommodate the Common Core Standards. The greatest content changes occurred in the development of whole number operations, geometry skills, and fraction concepts. Structural changes make *Math Trailblazers* 4th Edition easier for teachers, students, and families to implement, use, and understand in order to better help students develop deep conceptual understanding, a high degree of procedural skill and fluency, and the ability to apply the math they learn to solve problems both inside and outside of the classroom.