A high spatial resolution monthly mean climatological analysis of ocean hydrographic conditions (temperature and salinity) spanning the Mid-Atlantic Bight and Gulf of Maine region of the U.S. northeast continental shelf, and adjacent deep ocean, has been developed. The underlying observations for this Mid-Atlantic Ocean Climatological and Hydrographic Atlas (MOCHA) were obtained from the World Ocean Database (Boyer et al. 2009), the NOAA Northeast Fisheries Science Center database, and directly from local principal investigators whose data were not present, at the time of download, in the larger archives. The assembled data comprised 30,306,552 temperature and 10,258,727 salinity observations made between January 1864 and November 2009. Details of the analysis methodology are presented in Fleming (2016). In brief, the quality screened hydrographic profiles were mapped onto 57 standard depths and then interpolated onto a regular horizontal roughly 5-km resolution spatial grid using a loess filter weighted least squares approach based on the methodology of Ridgway et al. (2002). The adaptive local weights were dependent on horizontal distance, vertical distance, day-of-year, and ocean depth at the observation location so as to favor weighting in the along-isobath direction. The MOCHA analysis was a key data set used by Levin et al. (2018) to constrain a data-assimilative analysis of the mean and seasonal cycle of circulation in the Mid-Atlantic Bight. The resulting kinematically and dynamically constrained Mean Dynamic Topography substantially improved upon existing products available to the coastal satellite altimetry community. The MOCHA dataset is presented in a single NetCDF file adhering to CF-1.6 conventions. Boyer, T.P., J. I. Antonov , O. K. Baranova, H. E. Garcia, D. R. Johnson, R. A. Locarnini, A. V. Mishonov, T. D. O’Brien, D. Seidov, I. V. Smolyar, M. M. Zweng, (2009). World Ocean Database 2009. S. Levitus, Ed., NOAA Atlas NESDIS 66, U.S. Gov. Printing Office, Wash., D.C., 216 pp., DVDs. Fleming, N.E. (2016), Seasonal and spatial variability in temperature, salinity and circulation of the Middle Atlantic Bight, PhD, 336 pp, Rutgers University, New Brunswick, NJ, doi: 10.7282/T3XW4N4M Levin, J., J. Wilkin, N. Fleming and J. Zavala-Garay, (2018), Mean circulation of the Mid-Atlantic Bight from a climatological data assimilative model, Ocean Modelling, 128, 1-14, doi:10.1016/j.ocemod.2018.05.003 Ridgway, K. R., J. R. Dunn and J. L. Wilkin (2002). Ocean interpolation by four-dimensional weighted least squares - application to the waters around Australasia. Journal of Atmospheric and Oceanic Technology 19, 1357-1375.