This data release contains extended estimates of daily groundwater levels and monthly percentiles at 27 short-term monitoring wells in Massachusetts. The Maintenance of Variance Extension Type 1 (MOVE.1) regression method was used to extend short-term groundwater levels at wells with less than 10 years of continuous data. This method uses groundwater level data from a correlated long-term monitoring well (index well) to estimate the groundwater level record for the short-term monitoring well. MOVE.1 regressions are used widely throughout the hydrologic community to extend flow records from streamgaging stations but are less commonly used to extend groundwater records at wells. The data in this data release document the results of the MOVE.1 regressions to estimate groundwater levels and compute updated monthly percentiles for select wells used in the groundwater index in the Massachusetts Drought Management Plan (2019). The U.S. Geological Survey (USGS) groundwater identification site numbers and groundwater level data are available via the USGS National Water Information System (NWIS) database (available at https://waterdata.usgs.gov/nwis). Groundwater levels provided are in depth to water level, in feet below land surface datum. This data release accompanies a USGS scientific investigations report that describes the methods and results in detail (Ahearn and Crozier, 2024). Reference: Massachusetts Executive Office of Energy and Environmental Affairs and Massachusetts Emergency Management Agency, 2019, Massachusetts drought management plan: Executive Office of Energy and Environmental Affairs, 115 p., accessed September 2022, at https://www.mass.gov/doc/massachusetts-drought-management-plan The following are included in the data release: (1) R input file that lists the final site pairings (R_Input_MOVE1_Site_List.csv) (2) R script that performs the MOVE.1 and produces outputs for evaluation purposes (MOVE1_R_code.R) (3) MOVE.1 model outputs (MOVE1_Models.zip) (4) Estimates of daily groundwater levels using the MOVE.1 regression technique (MOVE1_Estimated_Record_Tables.zip) (5) Plots showing time series of estimated daily groundwater levels from the MOVE.1 technique (MOVE1_Estimated_Record_Plots.zip) (6) Plots showing time series of estimated daily groundwater levels from the MOVE.1 technique zoomed into the period of observed daily groundwater levels for the short-term site (Zoomed_MOVE1_Estimated_Record_Plots.zip) (7) Plots showing residuals (Residuals_WL_Plots.zip) (8) Monthly percentile table for 27 study wells (GWL_Percentiles_All_Study_Wells.csv)