Sterling St. John Jr., 69, a retired government economist who specialized in port operations and industrial development, died Monday at Montgomery General Hospital in Olney. He had suffered from emphysema.

Mr. St. John first came to Washington in 1935 as a staff member of the Foreign Trade Zones Board of the Department of Commerce.

During World War II, he served as chief of the port conditions section of The War Shipping Administration. He later worked in New York and then in Detroit before rejoining the federal government.

He worked for the old International Cooperation Administration, and then the Agency for International Development, from 1957 until his retirement in 1962.

Mr. St. John was born in Vineyard Haven, Mass. He earned a bachelor's degree from Randolph Macon College and a master's degree in business administration from the University of Pennsylvania.

He is survived by his wife, Beulah M., of the home in Silver Spring; a son, Anthony P., of Allentown, Pa.; two daughters, Merrily Hardisty and Leslie Anne Talkin, both of Washington; two sisters, Aimee Schrader, of Essex, Conn., and Holly Kemp, of Vineyard Haven, and five grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the Lung Association of Mid-Maryland Inc. in Rockville.