  We review entangled coherent state research since its first implicit use in
1967 to the present. Entangled coherent states are important to quantum
superselection principles, quantum information processing, quantum optics, and
mathematical physics. Despite their inherent fragility they have produced in a
conditional propagating-wave quantum optics realization. Fundamentally the
states are intriguing because they are entanglements of the coherent states,
which are in a sense the most classical of all states of a dynamical system.
