Scientific information is required to support the delineation of a continental shelf maritime zone extending beyond 200 nautical miles from shore. Application of Article 76 of the Convention on the Law of the Sea requires the use of geological, geophysical, and hydrographic measurements, as well as integrated interpretations to illuminate structures and processes of the shelf, slope, and deep-sea floor. Thirty-four (34) NOAA multibeam bathymetric mapping expeditions and 10 USGS geophysical research cruises were conducted as part of a 20-year governmental effort to delineate the outer limits of the U.S. extended continental shelf (ECS). The data from the U.S. ECS project continue to provide a wealth of scientific opportunity and the effort has produced a valuable public legacy of new and rescued datasets, data syntheses, interpretive products, and scientific publications. Research in support of ECS has enhanced scientific understanding of margins and deep ocean basins of the Atlantic, Pacific, Gulf of Mexico, Arctic and Bering Sea, including islands of the Pacific. Examples include primary discoveries of seamounts and gas plumes, advances in understanding the tectonic history of the Arctic basins, quantification of natural gas and hydrate systems, an astonishing landslide history of the Atlantic margin, a proposed Pacific mantle melt source, and a complex history of oceanic intra-transform spreading that influences subduction near the Mendocino triple junction on the California margin. This investment has also served as an example of interagency and multidisciplinary collaboration that helped to codify the National Ocean Mapping Exploration and Characterization (NOMEC) strategy. The NOMEC council coordinates the development of a national strategy for mapping, exploring, and characterizing the United States EEZ, and for enhancing opportunities for collaboration among interagency and non-United States Government entities. This presentation showcases just a sampling of the scientific discoveries and advances resulting from the interagency U.S. ECS effort, illustrating the breadth, depth and impact of work by USGS, NOAA, and our collaborative partners.