Emerson Plummer, a retired insurance salesman, died of heart failure Monday at Dorchester General Hospital. He was 75 and had moved to Cambridge from Essex in 1972 after his retirement from the Baltimore office of the Automobile Club of Maryland, where he worked for 23 years.

Services for Mr. Plummer were being held today at the Frampton-Hawkins-Eskow funeral establishment in Federalsburg.

The native of Brookview served in the Army Air Forces during World War II.

He was former master of the Roelma Lodge of the Masons in Sharptown and a member of the Scottish and York rites, the Middle River Square Club, the Chesapeake Forest of the Tall Cedars of Lebanon, the Eastern Shore Shrine Club and the Boumi Immediate Benefit Association.

He is survived by his wife of 55 years, the former Sadie Calloway; two daughters, Patricia P. Robinette of Fallston and Gloria V. Nethkin of Essex; a son, Kenneth E. Plummer of Cambridge; two brothers, Earl Plummer of Trenton, N.J., and Milton Plummer of Levittown, Pa.; four grandchildren; and four great-grandchildren.