The United States' implementation of the Montréal Process indicator of forest fragmentation presents a case study in the development and application of science within a criteria and indicator framework to evaluate forest sustainability. Here, we review the historical evolution and status of the indicator and summarize the latest empirical results. While forest cover fragmentation is increasing, the rate of increase has slowed since 2006. Most of the fragmentation in the western United States is associated with changes in semi-natural land cover (e.g., shrub and grass) while most of the eastern fragmentation is associated with changes in agriculture and developed (including roads) land covers. Research conducted pursuant to indicator implementation exemplifies the role of a criteria and indicator framework in identifying policy-relevant questions and then focusing research on those questions, and subsequent indicator reporting exemplifies the value of a common language and developed set of metrics to help bridge the gaps between science and policy at national and international scales.