Florence D. Hannabass, who retired from the National Security Agency in 1983 as head of the agency’s map library, died Dec. 31 at Powhatan Nursing Home in Falls Church. She was 91.

The cause was congestive heart failure, said her executor and friend, Frank Impala.

Miss Hannabass, a resident of Arlington County, spent 33 years in a variety of technical, staff and managerial positions at NSA headquarters in Fort Meade, Md.

After her retirement, she worked part time as a public relations specialist and cable television program assistant for the Arlington Central Library.

Florence Darline Hannabass, a native of Roanoke, was a 1943 graduate of Roanoke College. During World War II, she worked for two years in a chemical laboratory at a defense plant in Richmond. In 1947, she received a master’s degree in colonial American history from the University of Michigan.

After graduation, she taught history for several years at Wilson College in Chambersburg, Pa., and what is now Rockford University in Rockford, Ill., before settling in Washington.

Miss Hannabass served two terms as chairperson of the D.C. chapter of the Special Libraries Association’s Geography and Map Division and was the associate editor of the group’s bulletin. She was also a past museum director and treasurer of the Arlington Historical Society.

She had no immediate survivors.

— Megan McDonough