Long-term oceanographic observations made in western Massachusetts Bay at long-term site LT-A (42 degrees 22.6 minutes N., 70 degrees 47.0 minutes W.; nominal water depth 32 meters) from December 1989 through February 2006 and long-term site B LT-B (42 degrees 9.8 minutes N., 70 degrees 38.4 minutes W.; nominal water depth 22 meters) from October 1997 through February 2004 are presented here. The observations were collected as part of a U.S. Geological Survey (USGS) study designed to understand the transport and long-term fate of sediments and associated contaminants in Massachusetts Bay. The observations include time-series measurements of current, temperature, salinity, light transmission, pressure, oxygen, fluorescence, and sediment-trapping rate. About 160 separate mooring or tripod deployments were made on about 90 research cruises to collect these long-term observations. This report presents a description of the 17-year field program and the instrumentation used to make the measurements, an overview of the data set, more than 2,500 pages of statistics and plots that summarize the data, and the digital data in Network Common Data Form (NetCDF) format. This research was conducted by the USGS in cooperation with the Massachusetts Water Resources Authority and the U.S. Coast Guard. For more information on the field operations associated with data collection: http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1989-035-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1990-002-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1990-016-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1990-041-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1991-005-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1991-016-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1991-036-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1992-002-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1992-008-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1992-026-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=1992-029-FA 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