Salt marshes provide valuable services, such as protecting the coastfrom storms, removing excess nutrient pollution from water, and long‐term burial of carbon. Because sealevel is currently rising, salt marshes need to build up elevation at the same rate as sea level rise to survive.Human‐produced nitrogen pollution is rising in salt marshes, often increasing the growth of grass,which may cause the marsh to trap sediment more efficiently and build elevation faster. However, increasednitrogen may also decrease root growth and increase sediment microbial activity (which decomposessediment organic carbon to carbon dioxide), causing elevation‐building to slow down. It is unclear whetherthe addition of nitrogen affects the marsh's elevation‐building rate in a positive or negative way. Wefound that the effect of nitrogen on elevation‐building depends on location. Factors such as tidal inundationand residence time influence sediment water chemistry and, thereby, the response to excess nitrogen.Sulfide inhibits the uptake of nitrogen by plant roots and also microbial activity; thus, marsh locations withmore sulfide have diminished responses to nitrogen pollution. This knowledge may be used formanagement of marshes at risk due to nitrogen pollution.