 McClellan resigned his commission January 16 , 1857 , and , capitalizing on his experience with railroad assessment , became chief engineer and vice president of the Illinois Central Railroad , and then president of the Ohio and Mississippi Railroad in 1860 . He performed well in both jobs , expanding the Illinois Central toward New Orleans and helping the Ohio and Mississippi recover from the Panic of 1857 . Despite his successes and lucrative salary ( $ 10 @,@ 000 per year ) , he was frustrated with civilian employment and continued to study classical military strategy assiduously . During the Utah War against the Mormons , he considered rejoining the Army . He also considered service as a filibuster in support of Benito Juárez in Mexico . 
