Charles C. Diggs Jr., 75, a Michigan Democrat who served 25 years in Congress, where he helped found the Congressional Black Caucus and rose to become chairman of the House District Committee, died Aug. 24 at Greater Southeast Community Hospital after a stroke.

Mr. Diggs was elected to the House in 1954. He was the first chairman of the Congressional Black Caucus, serving from 1969 to 1971, and from 1973 to 1978, he was chairman of the House District Committee. He also was chairman of the African affairs subcommittee of what was then the House Foreign Affairs Committee.

During his years as committee chairman, he spearheaded the efforts that resulted in the District's receiving a Home Rule Charter. He also was instrumental in the creation of the University of the District of Columbia and in the movement to declare the Frederick Douglass home in Anacostia a national monument.

He resigned from Congress in 1980, two years after being convicted of 29 counts of operating a payroll kickback scheme in his office. In 1978, he was stripped of his committee and subcommittee chairmanships. He also was censured by the House.

During the trial and appeals, Mr. Diggs maintained that he was a victim of "selective prosecution" and that he was held to standards different from white colleagues.

After serving seven months of a three-year prison sentence, he returned to the Washington area. He settled in Hillcrest Heights, received a political science degree from Howard University and opened a funeral home business in Prince George's County.

Charles Coles Diggs Jr. was born in Detroit. His father was the wealthy, politically powerful owner and operator of the House of Diggs, once called Michigan's largest funeral home.

The younger Diggs attended the University of Michigan and Fisk University before serving with the Army Air Forces in World War II. After the war, he received a degree in mortuary science from Wayne State University and attended the Detroit College of Law.

Mr. Diggs, a licensed mortician, entered the family business in 1946, then served from 1951 to 1954 in the Michigan State Senate. He was elected to Congress in 1954 from Michigan's 13th District. He defeated seven-term incumbent George D. O'Brien in the Democratic primary and went on to win a landslide victory in the general election.

His district included downtown Detroit and some of the city's poorest neighborhoods. The district was one of the most Democratic in the country, and Mr. Diggs never had trouble winning reelection, even after his 1978 convictions.

Upon arriving in Congress, he was assigned to the Committee on Interior and Insular Affairs and the Veterans Affairs Committee. He immediately became active in civil rights activities and became a leading black spokesman. He called for speedy desegregation of public schools as well as desegregation of public transportation. In Michigan politics, he became a power in negotiations on redistricting after the 1960 U.S. Census. After that reapportionment, Michigan became the first state since Reconstruction to send two black representatives to the House.

On the Foreign Affairs Committee, he became an authority on Africa and a proponent of aid to emerging nations there. He became chairman of the District Committee in 1973 after the defeat of Rep. John L. McMillan (D-S.C.). CAPTION: CHARLES DIGGS JR.