Marshes are among the most important ecosystems in the world, but also are rapidly disappearing on a global scale, making it necessary but difficult to understand the processes behind natural marsh building. In this study, 210Pb-derived accretion rates are examined in a marsh at the Newport-River mouth, (NC), a location that has experienced ongoing emergence of new marshland over the past several decades. Accretion rates at all marsh-sampling sites shifted from slow sedimentation emblematic of the bay-bottom to rapid sedimentation that persisted as each site progressed from being an exposed mudflat to eventually becoming a newly colonized marsh table. This transition occurred asynchronously across the marsh and prior to vegetative colonization. This indicates that a physical transition occurred, likely due to a decrease in erosive processes such as wave-stirring. Creating a local regime of quiescence, these transitions promoted accretion and initiated marsh building that continues today.