Henry Randol McCollum is the son of James McCollum and his first wife Anna Randol. Henry was indeed killed on July 1, 1863 in the battle of Gettysburg. He was a member of Company H, 2nd Wisconsin Infantry as was his cousin Oliver E. Tillotson and his uncle Archibald McCollum. They all enlisted from Columbia County, Wisconsin and were mustered in at Camp Randall in Madison, Wisconsin.
Henry's father, James was also in the civil war in a different outfit as was another uncle, Oliver Perry Stevens and another cousin, Abram Eugene Stevens. James McCollum and Oliver Perry Stevens were both surgeons and Abram Eugene Stevens became a physician after the war.
Of the men listed above, Oliver Perry Stevens died and is buried in Maxincuckee, Marshall County, Indiana, Abram Eugene Stevens died and is buried in Argos, Marshall County, Indiana, Oliver Tilllottson died and is buried in Minneapolis, James McCollum died and is buried in or near Cresco, Iowa and Archibald McCollum died and is buried in Blue Earth County, Minneapolis.
The Wisconsin 2nd Infantry was a part of the Iron Brigade whose performance throughout the war was incredible. There were so many casualties during the battle at Gettysburg, that the Iron Brigade ceased to exist afterwards to all practical purposes. If you are interested in the war, the Wisconsin Historical Society has an incredible collection of material on the whole war and with those participants from Wisconsin in particular and the personnel at the society are very knowledgeable and helpful.
When the family was living in Wisconsin, they were mostly in Columbia County and centered on an area near Poynette, They moved to Wisconsin from Ohio with stops in LaGrange County, Indiana, Prior to Ohio they lived in Massachusetts, Pennsylvania and Nova Scotia. The residence in Nova Scotia was the result of John McCollum becoming a POW of the British during the revolution and sent to Halifax where he was incarcerated.