As part of the International Nuclear Energy Research Initiative project supported by the U.S. Department of Energy Office of Nuclear Energy, a collaborative team including Sandia National Laboratories, the Commissariat à l'Énergie Atomique in France, and industrial partner General Atomics constructed and operated a closed-loop system for demonstration of hydrogen production by the sulfur-iodine (S-I) process. The Integrated Laboratory-Scale experiment was conducted at General Atomics' San Diego facility. This paper will summarize project goals, results of the program, key challenges identified for the S-I process, and the lessons learned.