Michael Guinty S Military Record

My ggggrandfather, Michael GUINTY- was born in Ireland in 1841. His original name was Michael MCGINTY (family legend was that he changed his name to sound more German, the Irish were discriminated against quite often at that time), and he came to the US in 1847 with his parents. His parents died of Cholera about 1853, leaving him an orphan. He lived with another family in Chicago (after being by himself for a couple of years) and attended school, worked, and eventually joined the army at the age of 21. During the Civil War, he enlisted as a private, then to leutinent,then to captain. He enlisted in Mercer, Illinois, in 1861, and left the army in 1865. Not a bad army career for an Irish immigrant orphan! He is described as 5 ft, 10 inches tall, with black hair and brown eyes (the black hair is a dominant trait in our family), and a dark complexion. His origin is listed as Sligo, Ireland, but I've found out that often the origin is the last port the person departed from. I'm still looking for his siblings, hoping to find their true origins and ancestors.