We assimilate new multi-spectral retrievals of CO from the Measurement of Pollution in the Troposphere (MOPITT) instrument using the GEOS-Chem model to constrain North American CO emissions. The multi-spectral MOPITT retrievals (version v5) provide greater sensitivity to lower tropospheric CO over land and can capture pollution signals in the planetary boundary layer (PBL). We use the nested version of the GEOS-Chem model to conduct a high-resolution (0.5°x0.67°) inversion analysis over North America to quantify regional CO emissions. The emission estimates obtained from the MOPITT data are compared to those obtained using aircraft data from the Intercontinental Chemical Transport Experiment (INTEX-A).