North American beavers are ecosystem engineers in northern forested habitats. Impoundments from beaver dams can severely alter stream channel integrity, affecting trout productivity in low-gradient trout streams. To restore coldwater habitat, beavers and their dams have been removed from Class I and II trout streams within the Chequamegon-Nicolet National Forest in northern Wisconsin since the late 1980s. To understand the effectiveness of reducing beaver numbers, a Forest Service scientist and partners compared trends in beaver colony counts using fall flight colony location monitoring data from 1987 to 2013. Although beaver populations declined only on managed streams on the west side of the forest, managed and non-managed streams had declining beaver populations on the east side of the forest, indicating that a system change occurred in this area. Aspen stayed relatively similar through the same time period, so the decline is not believed to be related to decreased food availability. Results show the importance of long-term monitoring data to detect and interpret trends in management programs across large spatial and long temporal scales.