This volume presents papers on the topics covered at the National Academy of Engineering’s 2019 US Frontiers of Engineering Symposium. Every year the symposium brings together 100 highly accomplished early­career engineering leaders to share their cutting­edge research and innovations in selected areas. The 2019 symposium was hosted by Boeing in North Charleston, South Carolina, September 25–27. The intent of this book is to convey the excitement of this unique meeting and to highlight innovative developments in engineering research and technical work.