Elevation, vegetation, and soil salinity in restored and reference tidal marshes in California, Oregon, and Washington, 2023-2024.

We sampled marsh surface elevation, soil salinity, plant and macroalgal cover, plant composition, and plant species richness at 16 restored and 12 least-disturbed reference tidal marsh sites along the US Pacific coast during summer 2023 and summer 2024. Sites were located in the Tijuana River, Carpinteria, Elkhorn Slough, San Francisco Bay, Coos, Salmon River, Columbia River, Nisqually, and Skagit estuaries. Restored sites were 22 to 62 years old at the time of sampling; least-disturbed reference sites were usually located adjacent to restored marshes. We typically sampled three to four transects per site, measuring marsh surface elevation with RTK-GNSS, soil salinity from pore water extracted from near-surface sediments, and vegetation metrics in 0.25 m2 plots. In vegetation plots we recorded the cover of plants (usually to species level) and macroalgae (to major taxonomic group). This dataset accompanies a publication by Janousek et al. (2025) in Marine Ecology Progress Series which examines vegetation differences between older restored and reference marshes.