Philip M. Weightman was born in Vicksburg, Mississippi, in Jone 13, 1902. His father was Philip Mitchell Weightman, a contractor and butcher; his mother was Sarah Watts of Port Gibson, MS. In Vicksburg he attended St. Mary's Catholic School, the Cherry Street Public School, and Mrs. Johnson's School (during the summer months). Later he attended Sumner High School, at night, in St. Louis, MO.

In the fall of 1917, at the age of fifteen, Weightman joined the Amalgamated Butcher Workmen in St. Louis. He and his family had moved there from Vicksburg via Memphis in 1916. A year later, at sixteen, he cut his teeth in politics by organizing a get-out-the-vote drive in the old Fifth Ward, when his father, a precinct captain was taken ill. In the following years Weightman rose through the ranks in the packing houses of St. Louis and Chicago to respected stature in the labor movement.

At a St. Louis Labor Day Parade organized by the Butcher Workmen in 1918, Weightman experienced his first unpleasant act of discrimination. After the parade the union has a celebration and served food. He was standing in line when someone told him had to "get on the other line." This union attitude hurt him deeply; he left the event vowing that he would never join another union.

Following his marriage to Eulalia Mays in 1920, he worked for several packing companies, and, after an involvement with the Al Smith presidential campaign, moved to Chicago in 1930. In 1937 he helped to organize Local 28 of the Packinghouse Workers, CIO, and became Chief Steward in his plant. In 1943 he became First International Vice-President of the United Packinghouse Workers, a post that he held until 1948 when he joined the staff of the CIO's Political Action Committee (PAC). CIO President Philip Murray selected Weightman for a special assignment in Panama to reorganize the administrative structure of the Government Employees Union there. He served as a Field Director for CIO-PAC from 1948 to 1955, and when the AFL and the CIO merged in 1955, he became a Field Director of the newly formed Committee on Political Education (COPE). In 1960 COPE Director James L. McDevitt named him Assistant National Director of COPE.

Weightman was also involved in community and civil rights activities. He was a member of the Chicago Human Rights Committee, First Vice-President of the Chicago NAACP, and a founder of the Southern Christian Leadership Conference; and he often served as a consultant for the National Urban League and other groups. He worked tirelessly to increase black voter registration in the North and South, and formed alliances with other minority groups, in particular Puerto-Rican Americans and other Latino communities. His efforts on behalf of voter registration contributed to some crucial electoral victories. He played an active role in the Congressional elections of 1954, convincing his colleagues to emphasize economic as well as civil rights issues.

Among his notable achievements were the defeat of right-to-work proposals in California and Ohio, a record turnout of black voters for Senator Kefauver in Tennessee in 1959; helping build the overwhelming minority vote for John F. Kennedy in 1960; and upset New Jersey election of Richard Hughes for governor in 1961.

Upon his mandatory retirement in 1967 he was hired by the Office of Economic Opportunity as a Supervisory Labor Relations Specialist. He served as principal contact for those with questions concerning interpretation and application of labor-management agreements, unfair labor practices complaints, third party involvement in the agency labor relations program, and other related matters. Weightman retired completely from government employment in 1980.