This data set includes Conductivity-Temperature-Depth (CTD) and dissolved oxygen profile data that were collected along Washington State’s outer coast within Olympic Coast National Marine Sanctuary towards the northernmost extent of the California Current System. Measurements were made at fourteen hydrographic stations during mooring deployment, recovery, and maintenance cruises between the months of May and October from 2005–2023. The 792 CTD profiles were acquired using Sea-Bird Scientific 19 SeaCAT or 19plus SeaCAT CTD profilers with associated SBE-43 (Sea-Bird Electronics) or Beckman or YSI-type (Yellow Springs Instruments) dissolved oxygen sensors. The data were processed via Sea-Bird Scientific’s SBE Data Processing application using six of the modules in the following order: Data Conversion, Filter, Align CTD, Loop Edit, Derive, and Bin Average. These processing steps and associated methods are the same as those used to process CTD data that make up the Newport Hydrographic Line time series located off the central Oregon coast thus allowing for a direct comparison between the two regions. Station Name Latitude Longitude Water Depth (m, MLLW) Makah Bay (MB) MB015 48.3254oN 124.6768oW 15 MB042 48.3240oN 124.7354oW 42 Cape Alava (CA) CA015 48.1663oN 124.7568oW 15 CA042 48.1660oN 124.8234oW 42 CA065 48.1659oN 124.8949oW 65 Teahwhit Head (TH) TH015 47.8761oN 124.6195oW 15 TH042 47.8762oN 124.7334oW 42 TH065 47.8767oN 124.7967oW 65 Kalaloch (KL) KL015 47.6008oN 124.4284oW 15 KL027 47.5946oN 124.4971oW 27 KL050 47.5933oN 124.6112oW 50 Cape Elizabeth (CE) CE015 47.3568oN 124.3481oW 15 CE042 47.3531oN 124.4887oW 42 CE065 47.3528oN 124.5669oW 65

We thank all the captains, crews, and technicians who enabled the collection of these data, and NOAA’s Office of National Marine Sanctuaries for sustaining this monitoring program for more than two decades. Support for CMR, MRF, and BTC was provided by NOAA’s Climate Program Office (Open Funder Registry/FundRef number 100007298) through Climate Observations and Monitoring Program grant NA22OAR4310559.