A broad doming of the Gulf coastal plain between Jackson, Mississippi, and New Orleans, Louisiana is indicated by leveling surveys carried out in 1934, 1959, 1964, and 1969. The progressive arching over a distance of 275 km attains a maximum average rate of 3.4¿0.5 mm/yr relative to Jackson. Additional leveling in the area indicates that the observed pattern of movement could be elongate, with its major axis parallel to the coast. The observed uplift is consistent, at least in sign, with longer-term trends indicated by deformed terraces in Mississippi and Louisiana. Oil, gas, and water withdrawal mechanisms as well as systematic leveling errors appear inadequate to explain the wavelength and magnitude of the observed elevation changes. The pattern of uplift resembles that which might be expected from flexure due to sedimentary loading at the mouth of the Mississippi delta. Simple models of flexure of a thin elastic plate overlying a viscous half space caused by sediment loading during the Holocene do predict rates similar to those evidenced by leveling, if relatively low mantle viscosities (3.¿1019 Pa s; 1 Pa s=10 poise) are used. These observations may represent direct measurements of ongoing dynamic flexure at a passive continental margin.