Two years of Langley extrapolations made from the Southern Great Plains (SGP) site of the Atmospheric Radiation Measurement (ARM) Program using two very different RSS instruments and a NIST-derived irradiance scale show larger extraterrestrial solar irradiances in the 400 to 600 nm domain by as much as 4.5% compared to the Neckel and Labs <1984> data. Our results are more congruent with that of Thuillier et al. <1998a, 1998b> in this domain but do not show larger irradiances than the Neckel and Labs data at wavelengths less than 400 nm. In addition to the question of the true extraterrestrial solar spectrum, the data we present here are directly useful for the interpretation of spectral measurements calibrated with current National Institute of Standards and Technology (NIST) irradiance standards, for which we believe this represents the most extensive determination of the solar irradiance.