Pvt. Patrick Creegan, Co. M,

mustered in Sept. 5, 1861 in Westmoreland Co., discharged in March 1863.

Creegan was an Irishman born in County Leitrim in 1832, migrated to America in 1852, married his wife Ann O'Conner in 1853. He allegedly met his bride on the ship Mohill, during the voyage and they settled in Allegany Co, MD around Frostburg.

Not sure how he went from there to Westmoreland Co., PA for muster but after his service he went back home to Maryland.   Discovered this image in August 2013 while conducting searches on the internet for '100th Pennsylvania' references.   I found the image captivating on it's own merit but also because I hadn't seen it prior.   The image is posted by descendant, Karen Creegan Cooper on a family genealogy page here: 

http://midlandsroots.com/military-heroes/1850-1900-civil-war/

According to Michael Kraus, who has several images with the same photographer's backdrop, the image was taken in 1862 while the Roundheads were in Beaufort, SC--note 'Palmetto' trees, the symbol of South Carolina painted on backdrop. 

Close-up view of Pvt. Patrick Creegan, Co. M