Col. Sylvester F. Blackwell, 74, retired inspector general of the D.C. National Guard and a veteran of World War II and the Korean war, died Wednesday of cancer at Washington Hospital Center.

He was also a vice president and assistant chemist with Norris A. Dodson, a chemcial company here, for more than 30 years.

A native of Washington, he graduated from Armstrong High School and Howard University. Col. Blackwell then enlisted in the 142d Engineers, the District's National Guard.

After becoming captain and commander of the company in 1939. Col. Blackwell recruited personnel for the 372d Infantry. The company was put on active duty in 1940 and deactivated in 1946, at war's end.

In 1947, the colonel organized the 171st Military Police Battalion in the District.

That until fought in the Korean war after its 300 men were called to active service for 22 months.

After returing from Korea, Col. Blackwell began rebuilding the battalion, which became part of the District's National Guard Col. Blackwell retired from the D.C. National Guard as its inspector general in 1962.

He is survived by his wife. Ruby, of the home in Washington: two sisters, Edith Beal of Richmond, and Alfreda Jones, of Tampa, Fla.; a brother, Roland, of Washington, and several nephews and nieces.