The Cassidy family has a long history of fine carpenters and builders and Allen was no exception. Allen learned his trade by working with his father until 1933 when he moved to Brookville, N.B. In 1929 he married Mildred Folkins whom he had met two years earlier at a basket social in Norton. They moved to Boston in 1935 where he was employed by U.S. Gypsum, but returned to Norton in 1938 due to ill health. During World War II ‏(1939-42)‏, he worked at Camp Sussex where he was foreman of a construction crew of about 200 men.

On March 7, 1942 he joined the Royal Canadian Navy. He retired from the navy as a Chief Petty Officer in October 1945. For the decade following WW II, Allen was employed by various construction firms on projects in New Brunswick, Prince Edward Island, and Newfoundland. In 1956 he built the Connaught Street School in Fredericton and the following year joined the New Brunswick Department of Education as a school planner from which he retired in 1976.

Always interested in the family history, Allen had a prominant role in the production of the 1949 version of the Cassidy Family History. Allen and his wife faithfully attended family reunions and services at the Cassidy Lake church. From the information he obtained, Allen drew a layout of the cemetery at Cassidy Lake. In 1980 he built a replica of the homestead at Cassidy Lake and presented it to his granddaughter, Anne Renwick.

Allen enjoyed talking at length about Cassidy Family history and life at Cassidy Lake with anyone who would listen. Many such discussions were held between Allen and his Aunt Clara Ann ‏(Cassidy)‏ MacDowell, also an avid family historian.