Series I: Correspondence, Biography, and Speeches, 1939-1971 includes Welsh's personal and political correspondence (mostly incoming), notes, a poem, and speeches made prior to his departure for Africa. Also included is a short biographical sketch. Among Welsh's correspondents are W.E.B. Du Bois; Claude McKay; Langston Hughes; the writer Bryher; politician and diplomat W. Averell Harriman; A. Philip Randolph; Lewis Corey; Allan S. Haywood; Jay Lovestone, director of the Department of International Affairs, AFL-CIO; Clement K. Lubembe, deputy general secretary of the Kenya Federation of Labour; and Tom Mboya, general secretary of the Kenya Federation of Labour and Chairman of the ICFTU Area Committee for East, Central, and Southern Africa.

Series II: CIO, AFL-CIO, and Other Organizing Files, 1937-1974 consists of correspondence, minutes, telegrams, resolutions, lists, leaflets, programs, invitations, employment permits, leases, and addresses and speeches that provide insight into Welsh's early career as a labor organizer. Some materials document Welsh's work for the CIO from 1937 to 1955 as a field representative organizing workers in the North and South, as well as in the Panama Canal Zone. Other files concern his membership in the National Association for the Advancement of Colored People (NAACP) and his later union activities during the 1950s and 1960s. These activities included organizing drives to unionize black workers, an effort which contributed to the formation of the Negro American Labor Council.

Series III: International Confederation of Free Trade Unions (ICFTU) Files, 1958-1971 includes correspondence, telegrams, reports, agendas, circulars, speeches, photographs, documentation of financial transactions, and news releases. Of particular interest is material on Welsh's appointment as ICFTU representative in Africa and reports on union activities in Liberia, Kenya, Uganda, and Tanganyika (now Tanzania). Also included is a list of ICFTU field representatives in Africa, Asia, and Latin America; a draft of the Constitution of the Confederation of East African Trade Unions; a report on the First All-African Trade Union Conference; and records of the Pan-African Trade Congress held in Casablanca in 1961. Additional documents deal with CIA involvement in Kenya; the formation of the African Labour College in Uganda, which provided educational training for trade unionists in Africa; and the opposition to Tom Mboya's affiliation with the ICFTU by African countries that wanted to operate independently. The series also includes speeches made by heads of African states at a summit conference held in Addis Ababa, Ethiopia in 1963; a description of union activity and efforts to create a national trade union center in the Sudan; and financial accounts and a proposed program of organization and education within the Kenya Federation of Labour.

A substantial portion of the periodicals in Series IV: African Pamphlets and Periodicals, 1956-1972 concern trade union activities in East and West African countries. Most of the pamphlets relate to nonunion activities, but there are a few pamphlets published by the ICFTU, the International Labor Organization (ILO), and the United Nations. There are three folders of miscellaneous pamphlets and periodicals with no direct bearing on trade unions in Africa. These publications will serve researchers interested in the trade union movement from an African perspective.

The files in Series V: Clippings, 1956-1965 are a rich source of materials for research into African trade union activities. Most clippings include dates, but only a few include the names of the newspapers. One file is from the U.S. press.

The miscellaneous selection of issues in Series VI: African Newspapers 1955-1964 contains material relevant to trade union history in various African countries.

Series VII: Photographs is comprised of black-and-white photographs that document Welsh's work for the CIO, AFL-CIO, and other labor organizations in Panama, Africa, and the United States, especially during the 1950s and 1960s. The series contains group shots and portraits of Welsh, mostly from his years in Africa. The images from Panama include shots of various meetings, banquets, and speeches (including several from the March of Dimes), as well as photographs of seamen at the Panama Canal. There are also images from the Summit of Independent African States in Addis Abbaba, Ethiopia in May 1963 and three images from a folder labeled "Pictures - Africa," which consist of a group portrait featuring Welsh, an image of Welsh and another man holding up an embroidered shirt, and a candid photograph of Welsh and other men at the 14th Constitutional Convention of the CIO in 1952. Other images in the series are mostly photographs taken by news services of contemporary events in African nations during the 1950s and 1960s, as well as a few postcards and some group shots and portraits of various individuals.