The Central Valley, and particularly the San Joaquin Valley, has a long history of land subsidence caused by groundwater development. The extensive withdrawal of groundwater from the unconsolidated deposits of the San Joaquin Valley lowered groundwater levels and caused widespread land subsidence—reaching 9 meters by 1981. More than half of the thickness of the aquifer system is composed of fine-grained sediments, including clays, silts, and sandy or silty clays that are susceptible to compaction. In an effort to aid water managers in understanding how water moves through the aquifer system, predicting water-supply scenarios, and addressing issues related to water competition, the United States Geological Survey (USGS) developed a new hydrologic modeling tool, the Central Valley Hydrologic Model (CVHM; Faunt and others 2009). The data presented in this data release will be used to facilitate updates to the original CVHM, and represent aquifer-system compaction observations (measurements) using borehole extensometer data during 1958–2018 by USGS, California Department of Water Resources, San Luis and Delta-Mendota Water Agency, and Luhdorff and Scalmanini Consulting Engineers. For a more detailed description of borehole extensometer methods, please see Sneed and others (2013; 2018).