| National Founders Association | 1905-1911, bulk 1905-1909 | | LR001292 |
| National Organization for Women (NOW): Downriver Chapter Records, Parts I & II | 1971-1994 | | UR001227 |
| National Policy Association Records | 1930s-2003, bulk 1970s-2003 | | LR001816 |
| National Sharecroppers Fund Records | 1937-1985, bulk 1955-1972 | | LR000393 |
| National University Extension Association: Conferences and Institutes Division Records | 1952-1987 | | UR000638 |
| National War Labor Board Records | 1942-1947 | | LR000634_NWLB |
| Mercedes Nelson Papers | 1935-1971 | | LP000685 |
| New Detroit, Inc. Records | 1967-1975 | | UR000660 |
| Newspaper Guild Local 13 Records | 1934-1986 | | LR001311 |
| Newspaper Guild Local 22: Detroit Records | 1933-2007 | | LR000011 |
| Newspaper Guild Local 47: St. Louis Records | 1933-1966 | | LR000483 |
| Newspaper Guild Local 82: Pacific Northwest Newspaper Guild Records | 1950-1976 | | LR001600 |
| Newspaper Guild Records | 1933-1973 | | LR000401 |
| Tony Nicols Papers | 1938, 1941 | | LP001022 |
| Tatsuro Nomura Papers | 1920-1973 | | LP000736 |
| Harold Norris Papers | 1941-1968 | | UP000508 |
| Stanley and Margaret Collingwood Nowak Papers | 1928-1979 | | LP000003 |
| Harvey O'Connor Papers | 1919-1983 | | LP000245 |
| Rolland R. O'Hare Papers | 1957-1977, bulk 1972-1976 | | UP000826 |
| George O'Kon Scrapbook | 1916-1943, bulk 1930-1943 | | LP001184 |
| Francis O'Rourke Diary | 1936-1937 | | LP000518 |
| Office and Professional Employees International Union: Local 10 Records | 1929-1983 | | LR001316 |
| William Ogden Papers | 1937 | | LP000050 |
| William Oliver Papers | 1946-1984 | | LP000164 |
| John Oneka Papers | 1937-1964 | | LP000015 |
| Orange County Interfaith Committee to Aid the Farm Workers Records | 1963-1991, bulk 1982-1988 | | LR001546 |
| Oregon Federation of Teachers Records | 1974-2004 | | LR001598 |
| Organization in Solidarity with Central America Records | 1977-1995, bulk 1980s | | LR001627 |
| Charles Orr Papers | 1912-1970, bulk 1950-1970 | | LP000246 |
| Carrie Burton Overton Papers | 1856-1969 | | UP000323_CBO |
| Mary White Ovington Papers | 1854-1948 | | UP000323_MWO |
| Owosso Education Association Records | 1914-1968 | | LR000272 |
| Joseph F. Pagano Papers | 1938-1946 | | LP000012 |
| Frances D. and G. Lyman Paine Papers | 1953-1976, bulk 1953-1960 | | LP001439 |
| Francis Palmer Papers | 1933-1967, bulk 1944-1947 | | LP000861 |
| William Palmer Papers | 1932-1941, bulk 1933-1937 | | UP000693 |
| John Panzner Papers | 1922-1938 | | LP000009 |
| Frank A. Parker Papers | 1943-1949 | | UP000027 |
| Paul Parker Papers | 1939-1970, bulk 1950-1960 | | UP000423 |
| Rosa Parks Papers | 1955-1976 | | UP000775 |
| Lynn H. Parsons Papers | 1966-1971 | | LP001869 |
| Dolores Paskal Papers | 1960-1968, bulk 1960-1965 | | LP000237 |
| Oscar Paskal Collection | 1955-1964 | | LP000066 |
| Peabody Report | 1903 | | LR000000_PR |
| Raymond Peck Papers | 1937-1968 | | LP000392 |
| Jana Pellusch Papers | 1975-1976 | | LP000776 |
| People's Song Library Records | 1940-70, bulk 1940-55 | | LR000452 |
| Carl Person Papers | 1910-1920 | | LP000230 |
| Vincent Petitpren Papers | 1964-1967 | | UP000289 |
| Henry J. Pfaff Papers | 1973-1974 | | LP000672 |
| Norman E. Philleo Papers | 1880s | | LP000349 |
| Joseph Piconke Papers | 1942-1963 | | LP000126 |
| Fred C. Pieper Papers | 1936-1940 | | LP000165 |
| Alex Pilch Papers | 1967-1972 | | UP000579 |
| Pinkerton's National Detective Agency Reports | 1906-1907 | | LR000000_PNDA |
| Robert Pisarski Papers | 1949-1974 | | LP000814 |
| Irving Pokempner Papers | 1937-1959 | | LP000132 |
| James Poland Papers | 1934-1956 | | LP000361 |
| Helen and Mardy Polaner Papers | circa 1940-1969 | | LP001257 |
| Ethel Polk Papers | 1938-1939 | | LP001488 |
| Sam Pollock Papers | 1958 | | LP000111 |
| Philip D. Porter Papers | 1939-1947 | | LP000875 |
| Thomas E. Posey Papers | 1926-1977 | | LP001155 |
| Will Poyfair Papers | 1905-1922 | | LP000916 |
| Otto Pragan Papers | 1941-1961 | | LP000617_Pragan |
| Press Associates, Inc. Records | 1954-1980 | | LR000658 |
| Ada I. Pressman Papers | 1950-1985, bulk 1970-1985 | | LP001944 |
| Jacob Probe Papers | 1940-1942 | | LP000706 |
| PROD, Inc. Records | 1972-1979 | | LR000929 |
| Edward Purdy Papers | 1944-1968 | | LP001049 |
| James G. Pyrros Papers | 1943-1988 | | UP001940 |
| Quarry Workers International Union of North America Records | 1906-1914 | | LR001338 |
| Samuel Rabinovitz Papers | 1966-1979 | | LP001055 |
| Sophia Radlow Papers | 1948-1951 | | LP000764 |
| Philip Rahoi Papers | 1934-1968 | | UP000284 |
| Leo Ranco Papers | 1961-1979 | | LP000945 |
| Bonnie Lee Moss Rattner Papers | 1961-1997 | | UP001725 |
| Ray Howe Papers | 1959-1992, bulk 1968-1974 | | LP002130 |
| Esther H. Read Papers | 1976 | | LP001307 |
| Herman Rebhan Papers | 1976-1989 | | LP001791 |
| Richard Reist Papers | 1941-1968, bulk 1964-1967 | | LP000681 |
| Robert Repas Papers | 1914 | | LP000731 |
| Roy Reuther Papers | 1924-1971, bulk 1936-1971 | | LP001334 |
| Victor G. Reuther Papers | 1890-1980, bulk 1928-1980 | | LP000002_VGR |
| Victor Reuther Papers | 1936-1938 | | LP000002 |
| Victor Reuther: UAW New Directions Movement Papers | 1986-1991 | | LP000002_NDM |
| Irving Richter Papers | 1934-1988 | | LP000932 |
| Morris Riger Papers | 1936-1986 | | LP001484 |
| Blanche Rinehart Papers | 1949-1966 | | LP000114 |
| Harry Riseman Papers | 1930-1936 | | LP001076 |
| Matilda Robbins Papers | 1900-1963 | | LP000143 |
| Dalton Roberson Papers | 1970-1999 | | UP001735 |
| George Roberts Papers | 1933-1960 | | LP000038 |
| Archie W. Robinson Papers | 1927-1980 | | LP001355 |
| Remus Robinson Papers | 1928-1970 | | UP000447 |
| Robert N. Rockwell Papers | 1956-1966 | | LP000398 |
| Barry Roderick Papers | 1981-1983 | | LP001333 |
| Cecil Roeder Papers | 1937-1948 | | LP000184 |
| Marvin Rogoff Papers | 1960-1971 | | LP001082 |
| Sidney Rosen Papers | 1921-1980 | | UP001793 |