This data release is comprised of tidal marsh biomass data and spatial predictions of peak biomass and Julian day of peak biomass using data from the Landsat archive. Aboveground biomass dry weight of mixed-species plots (25x50 cm) at a tidal marsh in Willapa Bay, Washington were used to establish a relationship between biomass and tasseled cap greeness (TCG). The julian day of annual peak greenness and the value of annual peak greenness for 32 years at Bandon National Wildlife Refuge (NWR), Grays Harbor NWR, and Nisqually NWR was calculated by fitting a Gaussian function to the TCG values for a given year. The value of each 30 meter pixel is the Julian day of maximum predicted TCG or the maximum predicted TCG. There are 32 layers in the raster, each corresponding to the the years 1984-2015 (layer 1 is 1984, layer 32 is 2015). These data support the following publication: Buffington, K. J., Dugger, B. D., and Thorne, K. M. (2018). Climate-related variation in plant peak biomass and growth phenology across Pacific Northwest tidal marshes. Estuarine, Coastal and Shelf Science, 202, 212-221. https://doi.org/10.1016/j.ecss.2018.01.006