We have measured the degree of Faraday rotation towards 73 extra-galactic sources at low Galactic latitudes, predominantly within the first quadrant of longitude. The Faraday rotation towards extragalactic sources follows the trends of that towards pulsars, a fact which vindicates an initial assumption that the rotation arises mostly from within the Galaxy. When combined with the pulsar data, our data imply the existence of magnetic field reversals along several lines of sight. Extragalactic sources with l > 60° have rotation measures that are systematically larger than those for pulsars in the same region, which suggests that the structure responsible for the excess rotation must lie more distant than ~ 7 kpc.