This study examines the efforts of the Union and Confederate diplomatic agents to influence the events along the Rio Grande during the Civil War. The paper compares the successful accomplishments of Confederate agent Jose Quintero to the hindered maneuverings of the Union representatives, Leonard Pierce and M. M. Kimuey. Utilizing microfilmed sources from State Department records and Confederate despatches, the paper relates the steps Quintero took to secure the Confederate-Mexico border trade, obtain favorable responses from the various ruling parties in northern Mexico, and hamper the Union agents' attempts to quell the border trade.