Teacher evaluation systems have been a pillar of recent efforts to improve instruction and ensure that all students have access to effective educators. Chicago Public Schools (CPS) began revising its approach to teacher evaluation in 2006. An initial pilot, the Excellence in Teaching Project (EITP), launched in 2008. The current system, called REACH Students (Recognizing Educators Advancing Chicago's Students), represents a dramatic departure from the checklist system used prior to 2008. In the 2014-2015 school year, for the first time under the new system, almost all CPS teachers received an evaluation score. In Chicago and nationwide, these implementation efforts have prompted ongoing conversations about the implications of the new system for teachers, administrators, and students. The UChicago Consortium on School Research has been studying teacher evaluation in CPS from the initial EITP pilot to district-wide implementation of REACH. Studies have included annual surveys of teachers and principals, quantitative analysis of all available ratings, and qualitative interviews with educators and administrators. This retrospective highlights key findings and lessons learned in Chicago from 2008 to 2014.