Here is a curated list of primary sources for those researching the Congo Free State and the Congo Reform Movement, including direct links to access these materials:

Official Reports and Documents

1. General Act of the Berlin Conference on West Africa (1885)
   • The treaty formalising European colonial claims, including the establishment of the Congo Free State.
   • Full Text PDF
   • Archive.org Version
2. The International Association of the Congo
   • One source of these is located in the Liévin Jean Van de Velde (1850-1888) papers. Van de Velde was was a captain of the Belgian Army, active in the development and control of the Congo Free State.
   • Liévin Van de Velde papers
3. The Casement Report (1904)
   • Landmark report by British Consul Roger Casement, detailing firsthand accounts of atrocities in the Congo.
   • Full Text on Project Gutenberg
   • Archive.org Version
4. Reports of the Congo Free State Commission of Inquiry (1905)
   • Investigation by the Belgian commission into abuses following international pressure.
   • Archive.org version (translated)
5. Missionary Society Reports (Various Dates)
   • Reports from organisations like the American Presbyterian Congo Mission.
   • American Presbyterian Congo Mission archives

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Contemporary Newspapers and Periodicals

1. The Times (London) (Coverage from 1880s–1920s)
   • Frequently covered Congo Free State atrocities and the reform movement.
   • Times Digital Archive (subscription required)
2. The Manchester Guardian (Coverage from 1880s–1920s)
   • Regular articles exposing Leopold II’s regime.
   • Guardian archive
3. The West African Mail (1903–1914)
   • Edited by Edmund D. Morel, featuring numerous exposés on the Congo.
   • Morel Papers at the London School of Economics (LSE) Library
4. Reports in The New York Times (Coverage from 1880s–1910s)
   • American newspaper coverage of the international Congo reform movement.
   • New York Times archives

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Correspondence and Speeches

1. Leopold II’s Correspondence (1870s–1900s)
   • Letters revealing Leopold’s private strategies regarding the Congo Free State to Henry Morton Stanley.
   • AfricaMuseum Archives
2. Roger Casement’s Diaries and Correspondence (1903–1904)
   • Personal notes and letters.
   • National Library of Ireland Collections
3. Edmund D. Morel’s Letters and Speeches (1900s–1920s)
   • Letters and speeches advocating for Congo reform.
   • Morel Papers at the Bodleian Library

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Photographic Evidence

1. Congo Images (1890s–1900s)
   • Henry Morton Stanley images from his time in the Congo region.
   • Archive.org
2. Alice Harris’s Missionary Photographs (1898–1908)
   • From a recent museum exhibition.
   • International Slavery Museum, Liverpool (2015)

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Contemporary Literature

1. Joseph Conrad, Heart of Darkness (1899)
   • A fictional work reflecting Conrad’s firsthand experiences as a steamboat captain in the Congo.
   • Full Text on Project Gutenberg
2. E.D. Morel’s Books:
   • Affairs of West Africa (1902): Archive.org
   • King Leopold’s Rule in Africa (1904): Archive.org
   • Red Rubber (1906): Archive.org
   • Great Britain and the Congo (1909): Archive.org
   • The Black Man’s Burden (1920): Archive.org
3. Mark Twain, King Leopold’s Soliloquy (1905): Online here
4. Marcus R.P. Dorman, A Journal of a Tour in the Congo Free State (1905): Gutenberg
5. Frederick Starr, The Truth about the Congo (1907): Gutenberg
6. Booker T. Washington, ‘Cruelty in the Congo Country.’ Outlook, Vol.78, No.6 (8 October 1904), 375-377: Online here

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Missionary and Humanitarian Documents

1. Records of the Aborigines’ Protection Society (1890s–1910s)
   • Advocacy group fighting against abuses in the Congo Free State.
   • Bodleian Library, University of Oxford
2. Missionary Letters and Diaries (1890s–1910s)
   • Available through archives like the Council for World Mission or American Presbyterian Historical Society.
   • Presbyterian Historical Society Archives

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Maps and Geographical Data

1. Stanley’s Maps and Journals (1870s–1890s)
   • Explorer Henry Morton Stanley’s documentation during his expeditions in the Congo.
   • AfricaMuseum
2. Congo Free State Administrative Maps (1890s–1900s)
   • Maps detailing Leopold’s claimed territories, found in Belgian and European archives.
   • Archive.org

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Archival Collections

1. AfricaMuseum (Belgium)
   • Extensive collections of documents, photographs, and artifacts from the Congo Free State era.
   • AfricaMuseum
2. Belgian National Archives (1880s–1910s)
   • Colonial administration records, including annual reports and correspondence.
   • National Archives of Belgium
3. University Library and Museum Archives (1880s–1910s)
   • Collections like the Congo Reform Association Papers and personal correspondence of prominent British and American activists.
   • London School of Economics (LSE)
   • Merseyside Maritime Museum
   • Clark University
   • University of Chicago