Born in Lancaster County, Armstrong opened a studio in Marietta and began his career as an artist and teacher. The artist later maintained a bustling studio and gallery on Orange Street in Lancaster City. He likely trained in Philadelphia, where he was no doubt influenced by Thomas Sully and other portrait artists of the era. This large scale portrait is one of only four hand-signed and dated works (on the reverse) by the artist. The sitter, David Cockley (1802 – 1861), was the first president of the Lancaster Locomotive Works.