Collection
- Michigan Photographers Society photographs, circa 1880-19251
- Mullett Family papers, 1665-1924 (majority within 1825-1924)1
- Oliver Lyman Spaulding papers, 1861-19211
- Patterson Family papers, 1825-19311
- Penn Central Transportation Company Records, 1835-1981 (majority within 1835-1960)1
- Post Family Papers, 1882-19731
- Prohibition National Committee (U.S.) records, 1872-19721
- R. R. Rives photograph collection, 1940, 1948, undated1
- Ralph W. Muncy papers, circa 1830-19921
- Raymond J. Smit Papers, 1960-19771
- Richardson Family Papers, 1864-19661
- Rinsey family papers, 1856-1950 (majority within 1913-1928)1
- Rowe Family Papers, 1840-1990 (majority within 1840s-1940s)1
- Rudolph E. Reichert Papers, 1907-2004 (majority within 1907-1962)1
- Russell V. Judson Papers, 1913-19751
- Ruth Bordin papers, 1940-1992 (majority within 1980-1992)1
- S. Alicia Poole papers and photographs, 1860s-1950s1
- S. Vern Taylor papers, 1833, circa 1860-19141
- Squier Family papers, 1843-19771
- Standish Backus papers, 1919-19421