System identification is the process of developing or improving a mathematical representation of a physical system using experimental data. Over the past decade, several system identification techniques have been developed within different disciplines. This text/reference brings together the significant advances over the past decade into a single unified source -- with common mathematical notation that will enable readers from a variety of engineering areas -- e.g., aerospace, electrical, civil, and mechanical engineering --to apply system identification to engineering systems. Focuses on the three types of identification in engineering structures -- modal parameter identification; structural-model parameter identification; and control-model identification.