The Engineering Research and Development Center (ERDC), part of the U.S. Army Corps of Engineers (USACE), has been championing a pioneering program called the Engineering With Nature® (EWN®) initiative, which aims to promote the use of nature-based solutions (NBS) for coastal and fluvial flood risk management. As part of the EWN program, ERDC initiated a proving ground (PG) concept under which USACE districts and divisions may elect to prioritize, where possible, NBS pilot tests or projects, gather data, and improve upon existing EWN tools and techniques. This paper provides a review of the EWN PG process and key lessons learned.