Rising sea levels, severe extreme weather events, and rapid coastal development pose huge threats to US coastlines. Shoreline armoring is a common way to protect coasts from damage and erosion due to wave energy and weather events. However, hard structures built to protect shorelines often lack resilience, are not readily adaptable to changing conditions, and do not self-repair after disturbances. Further, armored shorelines support less diverse ecology than natural shorelines. As coastal development increases, so does the prevalence of shoreline armoring. Informed, sustainable decisions about coastal stabilization and development must be made moving forward, and informed decisions require data. Using ArcGIS, I analyzed shoreline data from NOAA’s Environmental Sensitivity Index to provide an updated estimate of the extent of shoreline armoring on US coasts. Results show that approximately 28,379 km of US shoreline is armored, about 10% of the total shoreline surveyed, and armoring percentages vary drastically between states. The data also reveal the most common type of shoreline armoring is sheltered, solid man-made structures like seawalls and piers. My analysis of the NOAA data revealed that advances in shoreline mapping methods and technologies have created discrepancies between current estimates of shoreline hardening and past estimates, making it problematic to compare the two. The ability to observe changes in shoreline hardening over time is critical to appropriate assessment and management of the socio-ecological impacts of future shoreline hardening.