Excel files have percentage impervious cover estimates for the Chesapeake Bay region from 30 m 1 m data for six assessment units - 12-digit hydrologic units (watersheds), the riparian zones for the same watersheds, and four square lattices with cell sizes of 40, 2756, 5625, and 22500 ha. There is an excel file for each assessment unit. These data were used to produce the results in Table 2 of the association publication (https://doi.org/10.1016/j.isprsjprs.2018.09.010). This dataset is associated with the following publication: Wickham, J., N. Herold, S.V. Stehman, C.G. Homer, G. Xian, and P. Clagget. Accuracy assessment of NLCD 2011 impervious cover data for the Chesapeake Bay region, USA. ISPRS Journal of Photogrammetry and Remote Sensing. Elsevier BV, AMSTERDAM, NETHERLANDS, 146: 151-160, (2018).