The QSO 3C 48 and its host galaxy constitute a nearby template object of the proposed merger-driven evolutionary sequence from ULIRGs to QSOs. In this contribution multi-wavelength observations and N-body simulations studying the structural and compositional properties of this late-stage major merger will be presented. Key questions addressed will be the nature of the apparent second nucleus 3C 48A and absence of a counter tidal tail. The results will be used to review the role of 3C 48 in the ULIRG-QSO evolutionary scenario.