In recent years, governors, chief state school officers, business leaders, and college faculty have grown increasingly concerned that American students are not adequately prepared either for college or for the workforce. Governors and chief state school officers understood that the changing economy and persistent achievement gaps required a dramatic shift in academic expectations. Further, they realized their states were no longer well served by a system in which each state had its own standards for what students should know and be able to do. In 2008, to better prepare all students for college and the workforce, governors and chief state school officers embarked on an historic, state-led effort to create a common core of academic standards in English language arts and mathematics for grades kindergarten through 12 (K-12). They insisted that the standards be based on research and evidence, be internationally benchmarked, and be aligned with college and workforce expectations. The National Governors Association Center for Best Practices (NGA Center) and the Council of Chief State School Officers (CCSSO) led the effort and, in June 2010, the NGA Center and CCSSO released the newly developed Common Core State Standards (CCSS) in arts and mathematics for K-12. As of September 2011, 44 states, the District of Columbia (D.C.), the U.S. Virgin Islands, and the Northern Mariana Islands, serving more than 80 percent of the nation's K-12 student population, had adopted the new standards in both English language arts and mathematics. The development and widespread adoption by states of the CCSS are an historic milestone in American education. Effectively implementing the CCSS in schools and K-12 classrooms has the potential to transform education in the United States by narrowing achievement gaps and ensuring that every student graduates from high school ready for college and work. Implementing the CCSS will be challenging because it will require significant changes in instruction, assessment, educator preparation and development, curriculum and materials, and accountability measures. Much of the work pertaining to implementation of the CCSS will be done in schools and classrooms by teachers and principals and their districts. Nevertheless, governors and other state policymakers can play a critical leadership role in supporting implementation of the CCSS. Governors' authority over education and the tools with which they can take action vary considerably from state to state, yet all governors should consider taking the following actions to support implementing the CCSS: (1) Communicate a vision for reform; (2) Identify performance goals and measure progress; (3) Engage key leaders from education, business, and philanthropy; (4) Build educator capacity; (5) Lead transitions in state assessments and accountability policy; (6) Support local development and acquisition of new curricula and materials; and (7) Maximize resources and share costs. Appended are: (1) A Sample Tool to Organize State Policy Decisions Pertaining to the Implementation of the Common Core State Standards; and (2) Educator Capacity Worksheet. (Contains 30 notes.)