We obtain exact analytical results for the evolution of a 1+1-dimensional Luttinger model prepared in a domain wall initial state, i.e., a state with different densities on its left and right sides. Such an initial state is modeled as the ground state of a translation invariant Luttinger Hamiltonian H λ with short range non-local interaction and different chemical potentials to the left and right of the origin. The system evolves for time t > 0 via a Hamiltonian H λ ′ which differs from H λ by the strength of the interaction. Asymptotically in time, as t → ∞, after taking the thermodynamic limit, the system approaches a translation invariant steady state. This final steady state carries a current I and has an effective chemical potential difference µ + − µ − between right-(+) and left-(−) moving fermions obtained from the two-point correlation function. Both I and µ + − µ − depend on λ and λ ′ . Only for the case λ = λ ′ = 0 does µ + − µ − equal the difference in the initial left and right chemical potentials. Nevertheless, the Landauer conductance for the final state, G = I (µ + − µ − ), has a universal value equal to the conductance quantum e 2 h for the spinless case.