This study focuses on the identification of carbon monoxide (CO) released during the forest fires that took place primarily in Montana and Idaho during the summer of 2000. We focus our analysis on the most intense period of the fires during the second half of August. During that period, the MOPITT instrument onboard the EOS-Terra platform collected extensive measurements of CO. A simulation of the dispersal of the CO from the fires, constrained by the AVHRR observations of fire location and extent, clearly identifies the affected regions. The model results are compared with the CO observations from the COBRA experiment flight on August 19. Using these various data, we are able to identify the transport of the CO plume originating from the fires. In particular, it is shown that the CO travels eastward from the fires, reaching as far as the East coast and the Gulf of Mexico in a few days. Although the distribution of CO over the U.S. is clearly a combination of a variety of sources it is found that wildfires are a strong component of the summer tropospheric CO.