This book is meant to provide the tools necessary to begin doing research involving crossed product C∗-algebras. Crossed products of operator algebras can trace their origins back to statistical mechanics, where crossed products were called covariance algebras, and to the group measure space constructions of Murray and von Neumann. Now the subject is fully developed with a vast literature. Crossed products provide both interesting examples of C∗-algebras and are fascinating in their own right. Simply put, a crossed product C∗-algebra is a C∗-algebra A⋊αG built out of a C∗-algebra A and a locally compact group G of automorphisms of A. When the C∗-algebra A is trivial, that is, when A is the complex numbers, then the crossed product construction reduces to the group C∗-algebra of harmonic analysis. In fact, the subject of crossed product C∗-algebras was introduced to me as the harmonic analysis of functions on a locally compact group taking values in a C∗-algebra. This is a valuable