John D. Buenker describes the boss-immigrant-machine complex of nineteenth-century America, how it developed, and the services it provided for the newly-arrived immigrant. His important new finding is that the so-called “urban political machine” and “boss,” long objects of disdain, were in fact major sources of support for a vast amount of reform legislation during the Progressive Era. The outlook and philosophy of programs that are now considered liberal, Mr. Buenker concludes, largely originated with the urban machine politician and what today would be called the ethnic working class.