Christopher Phillips chronicles Grant's entrance into the War:
After graduating from West Point, Grant married the daughter of an affluent Missouri slaveholder and, after an undistinguished and often drunken army career, left to farm unsuccessfully on a rocky piece of Missouri timber that his father-in-law gave him. (Appropriately, Grant named it "Hardscrabble.") Grant was even more ambivalent about slavery than his father -- enough to free the only slave he ever owned (given to him by his wife's father), but he was not sufficiently opposed to it to deter him from hiring slave field hands or sell his wife's domestic servants. Or to drive him from the Democratic Party, or even from the slave states. Or to remain largely politically uninformed. Eventually, Grant's poor head for business and ineptitude at farming forced him, debt-ridden, to seek refuge in Galena, in extreme northern Illinois, where he clerked in his father's store only months before the war began.There, the nation's ambition found him despite his best efforts. A veteran of the Mexican War (which he had opposed), Grant was the only man in town with military training, much less experience. He was soon beset by prominent Galenans, mostly Republicans who did not know the shut-mouthed Grant's politics, to lead its men into battle. He was unwilling to accept a volunteer commission, especially a subordinate one, and organized a company of volunteers and led them to the state capital, Springfield, where he helped to organize and train the thousands of men arriving daily.Unsatisfied with the volunteers, Grant appealed to Nathaniel Lyon in St. Louis (where he witnessed the fallout from the Camp Jackson affair) as well as George B. McClellan in Cincinnati for a commission in the Regular Army. When none came, he accepted the colonelcy of the 21st Illinois Volunteers, and soon marched them westward to Missouri, already plagued by warfare.