Structural movement monitoring can distinguish between seasonal movements and the more threatening progressive movements. Measuring changes in crack width, settlement, tilting, and deflection for at least 1 year can aid in conservation decisions. The author references projects from his 12 years of field experience in structural monitoring of historic structures and prehistoric ruins throughout the United States funded by the Department of the Interior, National Park Service. The effectiveness of various monitoring methods is discussed. Structural monitoring can save money and prevent unnecessary structural modifications by determining that some apparent structural defects do not require repair.