The persistence length of DNA has been studied for decades; however, experimentally obtained values of this quantity have not been entirely consistent. We report results from Brownian dynamics Simulations that address this issue, validating and demonstrating the utility of an explicitly double-stranded model for mesoscale DNA dynamics. We find that persistence lengths calculated from rotational relaxation increase with decreasing ionic strength, corroborating experimental evidence, but contradicting results obtained from wormlike coil assumptions. Further, we find that natural curvature does not significantly affect the persistence length, corroborating cyclization efficiency measurements, but contradicting results from cryo-EM.