Mary Elizabeth (Betty) Appleton, 71, a retired research assistant in the Naval Air Systems Command of the Navy Department, died June 4 at the Hawthorne Lodge nursing home in Hillsboro, Ill. She had suffered a series of strokes.

Miss Appleton was born in Hillsboro. She graduated from MacMurray College in Jacksonville, Ill., in 1931 and then taught in schools in the Hillsboro area.

She moved to Washington in 1941. From 1942 to 1949 she was secretary to the president of Washington Petroleum Products Inc.

She then began her career in the Navy Department in 1949 and worked first as a secretary in the Bureau of Aeronautics. She then did public relations work in the Office of Naval Research. Her last assignment before her retirement in 1973 for reasons of health was as a historical research assistant in the Naval Air Systems Command.

During her years in Washington, Miss Appleton was a member of the Sixth Presbyterian Church. She was president of its board of trustees and a member of the Mission Society and the Singles Club. She lived in the Presbyterian Home in Washington before moving to the Hawthorne Lodge facility in Hillsboro about two years ago.

Survivors include two brothers, Henry, of Benton, Ill., and Robert, of Hillsboro.