We use the worm-like chain as a first-principles model to study single molecule experiments of double stranded DNA subject to constant plug, elongational, and shear flows. The steady-state configurations of the polymer correspond to a locally defined potential and result in a path integral description of the canonical partition function. The parameters of this model are consistent with previous theory and experimental measurements. The time averaged mean extension reproduces experimental results and compares well with computationally more expensive Brownian dynamics simulations of reduced models. (C) 2003 Elsevier B.V. All rights reserved.