These lecture notes deal with the behavior of elastic bodies subject to small displacement gradients, namely their linearized elastic response. The framework for describing the nonlinear response of elastic bodies is first put into place and then the linearization is carried out to delineate the status of the linearized theory of elasticity. Easy reading for upper-division and first-year engineering students is provided by a balanced combination of mathematical rigor and physical understanding. This lecture note grew out of a course that the author regularly teaches to undergraduate mechanical engineering students.