Dorothea deSchweinitz, 89, a retired federal government employe who was active in historic preservation projects in Georgetown, died Thrusday at Alexandria Hospital after a stroke.

Miss deSchweinitz helped found the Historic Georgetown Corp. in the early 1950s. The organization seeks to preserve historic buildings in Georgetown. Miss deSchweinitz was the corporation's president in the 1960s and served as a vice president until her death.

During her years with the organization she helped direct the successful drive for the passage in 1950 of the Old Georgetown Act by Congress. She also helped prevent the demolition of the Thomas Sim Lee corner at 30th and M streets in Georgetown.

Miss deSchweinitz was born in Nazareth, Pa., and reared in Bethlehem, Pa. She worked for the Philadelphia Board of Public Education, was an official of the Pennsylvania State Employment Service, and was a regional official of the National Labor Relations Board in Pennsylvania before moving here in 1940.

During World War II, she was an official of the War Production Board's labor-management relations committee. She later worked for the Wage Stabilization Board. She retired from the government in 1953.

Miss deShcweinitz was a 1912 graduate of Smith College and earned a master's degree in economics at Columbia University. She was awarded the Smith College Medal in 1974 for her work in government and for Smith College.

She was president of the National Vocation Guidance Association in 1925. She was the author of four books on employment and business.

Survivors include a sister, Louise deSchweinitz Darrow of Kansas City, Kansas.