The active layer data available here has been collected as part of a collaborative monitoring project between the US Geological Survey, Yukon River Inter-Tribal Watershed Council, and Yukon River Basin communities known as the Active Layer Network (ALN). The active layer is the layer of soil above the permanently frozen ground (permafrost) that thaws during the summer months and freezes again in the autumn. By measuring the depth of the active layer in the late summer at the time of maximum thaw, we are able to better understand the effects of a warming climate on permafrost. ALN monitoring sites were installed across the Yukon River Basin, in Alaska and Canada, in 2009 and 2010. Each monitoring site consists of a 45 meter by 45 meter grid and sensors. Active layer depth measurements are taken every 5 meters across the grid resulting in 100 measurements made each year. Sensors installed at each location include soil moisture, soil temperature, and air temperature sensors. Sensor data is collected throughout the year and downloaded annually. Active layer depth measurements and sensor data are presented here.