Newspaper and magazine articles often provide details about Supreme Court justices, cases, and the parties involved. Most of the following historical and retrospective news databases are available via the Gelman Library.
Some researchers will find Justices' personal papers valuable for providing insight into decisions. The following source gives information on where Justices' personal papers are kept and the relative size of each collection:
Lee Epstein, Jeffrey A. Segal, Harold J. Spaeth & Thomas G. Walker, Table 5-11 Locations of Justices’ Personal Papers, in The Supreme Court Compendium: Data, Decisions, and Developments 476-84 (6th ed., 2015). Location: Ready Reference, 1st Floor. KF8742 .S914 2015.
The Library of Congress holds many Justices' papers in the Manuscript Division. Search the online Finding Aids for more information.
Note: Justices are not required by policy or statute to make their private papers available:
"Chambers papers are not part of the official records of the federal courts, and they remain the private property of the judge or the judge’s heirs. Disposition of those papers is the judge's or heirs' prerogative. Neither federal statute nor the policies of the Judicial Conference of the United States make any provision for preserving federal judges’ papers."