"M. R. McClennan ... distinguished himself by his superior courage and gallantry. "

- Col J. Warren Keifer, 138th PA

Before the Civil War, Matthew Robert Mcclennan worked at an iron works and in a print shop. During the war, he commanded the 138th Pennsylvania Volunteers. He and his men spent the first part of the war protecting the railroad lines from sabotage by Confederate sympathizers. Mcclennan later participated in several battles, including the Wilderness, Spotsylvania, and Cold Harbor. He was wounded at the Battle of Mine Run, Virginia in 1863. He eventually rose to the rank of Brigadier General by the end of the war.

After the war, Mcclennan went back to the printing business, becoming a partner in a print shop on Main Street in Norristown. He was active in the business until his death in 1872.