In their proposals to join the Math in Common (MiC) initiative, staff from each of the 10 participating districts acknowledged that the shifts required to implement the Common Core State Standards for Mathematics (CCSS-M) (NGA Center & CCSSO, 2010) would be a huge lift for teachers. They knew that mathematics teachers would be required to take up new, sometimes foreign ways of doing their work with students. Learning to provide useful, impactful professional development (PD) to support teachers in this process would become a primary focus of MiC. This report describes some of the more common roadblocks that MiC districts faced in their early years of CCSS-M implementation, and routes that the districts took around the roadblocks in order to support teacher and student learning. This report also includes brief vignettes, in "The View from the Field" text boxes, of districts' practices, to more clearly illustrate some of these roadblocks and the routes around them.