Home State: Pennsylvania
Command Billet: Commanding Regiment
Branch of Service: Infantry
see his Battle Report
Appointed Captain, Company B, 107th Pennsylvania, 20 February 1862.
On the Campaign
At the beginning of the Maryland Campaign, Colonel McCoy and Major Forney were absent sick. Lieutenant Colonel McAllen accompanied the column but was "too feeble to keep the field", so the command devolved on Captain MacThompson.
The rest of the War
In January 1863, Major Forney died and Captain Mac Thompson was commissioned to succeed him. Subsequently, Lieutenant Colonel McAllen, on account of his feeble state of health, resigned, and was succeeded by Major MacThompson as Lt. Colonel.
Colonel McCoy was again absent with illness after Chancellorsville, and MacThomson had command on the Gettysburg Campaign. He left the field after the second day's fighting there (July 2) "prostrated by severe duty".
He was honorably mustered out 13 July 1865.
References & notes
Source: Bates, Samuel P., History of the Pennsylvania Volunteers, 1861-65, Harrisburg, 1868-1871.; Extracted online at the Pennsylvania in the Civil War site; and
Heitman, Francis Historical Register and Dictionary of the United States Army 1789-1903, Washington, US Government Printing Office, 1903.
Is his middle name McLean?