I did indeed find out more about Maj. John Harritt. His sons were Augustine and John Hughes Harritt. Augustine enlisted in the Army and died in FL in 1839 "fighting Indians" according to the NARA. John Hughes Harritt fought in the Mexican War and ended up in CA. There was no record that either one of these men had children. Maj. John Harritt was too young for the Revolutionary War and too old for the War of 1812. He was part of the Maryland Militia that could be called up to defend the State or the Country if needed. There is no evidence,according to NARA that he was ever involved in any conflict. There were, however, a number of other "John Harritts" (with the name Harritt spelled variously) from different Harritt families scattered about the nation, to whom your grandson might be distantly related. They lived in NC, KY, OH, IN, NB and CA that I am aware of and their descendants may have lived in other southern states as well.