The National Equal Justice Library at Georgetown Law Library has the most comprehensive collection of manuscript materials documenting the history of the Office of Economic Opportunity's legal services program, which later became the Legal Services Corporation.
However, there exist many other manuscript collections documenting different aspects of the history of legal services in the United States across repositories in the United States. Below are just a few collections, others can be discovered through WorldCat, ArchiveGrid, or targeted searches at local repositories that are not incorporated into these union catalogs.
Freedmen's Bureau: The records of the Freedmen's Bureau are at the National Archives.
The Arthur van Briesen Papers are at Princeton University Libraries.
The records of the Office of Economic Opportunity are at the National Archives, including at regional facilities.
The record of the CRLA are at Stanford University Libraries.
The records of the Philadelphia Legal Aid Society are at Temple University.
The National Archive of Clinical Legal Education, located at Catholic University, also includes a number of relevant oral history interviews.