William S. Dahlen Sr., retired building engineer for the former United States Fidelity & Guaranty Co. building in downtown Baltimore, died of cancer Thursday at a hospital in Beech Grove, Ind. He was 80.

Mr. Dahlen, a longtime Linthicum resident, had lived since 1995 in Franklin, Ind.

Born in Baltimore and raised in Walbrook, Mr. Dahlen attended Gwynns Falls High School. During World War II, he enlisted in the Army and as an artillery man, served with the 106th Infantry and saw action at the Battle of the Bulge. He was discharged in 1945 with the rank of sergeant.

Mr. Dahlen married Barbara L. Swiggett in 1947 and the couple settled in Linthicum.

A metal worker by trade, he worked for Lloyd E. Mitchell Co. and Riggs Distler before being named building engineer for the United States Fidelity & Guaranty Building, now the Legg Mason Building.

Mr. Dahlen was a former parishioner and board member of Linthicum United Methodist Church. He had also been a district commissioner in Maryland for the Boy Scouts of America, and was a member of the 106th Infantry Division Association.

He was an avid woodworker and enjoyed building dollhouses in his basement workshop. He was also interested in genealogy and was an Orioles and Colts fan.

Services will be held today in Franklin.

Mr. Dahlen is survived by his wife; two sons, William S. "Bud" Dahlen of Pasadena and David B. Dahlen of West Glacier, Mont.; a sister, Dorothy Kavalasky of Baltimore; and five grandchildren.