Robert E. Brown's papers include research notes from the American colonial period, and professional correspondence from his career as a historian.

The research notes series are divided into three groups, (Massachusetts, New York City, and Virginia) which correspond to three of his books: Middle Class Democracy and the Revolution in Massachusetts, 1691-1780, Carl Becker on History and the American Revolution, and Virginia, 1705-1786: Democracy or Aristocracy? The bulk of the notes were taken in longhand by Brown from approximately 1950 to 1970; some were written by his wife, B. Katherine Brown. At the end of each entry the source, related sources to be checked, and personal observations are recorded.

Brown's notes on Massachusetts cover the years 1643 to 1894 but emphasize the revolutionary period. Entries are arranged alphabetically by subject. They discuss colonial government, society, regulations, prominent individuals and the common man. Notes in the addendum relate to his research methodology. Brown used these notes in writing his book Middle Class Democracy and the Revolution in Massachusetts, 1691-1780, which expounds on the theory that the colonists were primarily middle-class property owners who went to war against England to preserve the status quo rather than to establish new institutions and increase individual rights.

The research notes on New York City are divided into three sub-series: Freemen Admitted Prior to 1783, Freemen Admitted after 1783, and a Summary of Occupations. Entries are filed alphabetically by the individuals' last name in the first two series, and alphabetically by occupation in the last. Brown used the data included in these notes in his book Carl Becker on History and the American Revolution, in which he concluded that freemanship was not exclusive, as Becker implied, but rather was required for anyone engaged in a manual or professional occupation.

The notes on Virginia are grouped into four sub-series: Subject Entries, Geographical Entries, Chronological Entries and an addendum on his research methodology. They contain information relating to Virginia's people, laws, government and religion from 1645-1856. The election process, particularly in the late 1700s, is covered extensively. Plantation life, the role and living conditions of overseers, military records, plays and comments by colonists on gaming, and land acquisitions by George Washington are also noted. On these notes Brown based his book Virginia, 1725-1786: Democracy or Aristocracy?, in which he extended his thesis on middle-class democracy to Virginia.

The Correspondence series documents Brown's professional career from his graduate assistantship at the University of Wisconsin through his retirement from Michigan State. In addition to correspondence, these files contain reviews, articles, speeches, publishing contracts and other papers relating to his professional life as a historian. The papers have been annotated by Brown in some instances, and also include works and correspondence of his wife, B. Katherine Brown. The series is arranged chronologically starting with September 1940 and concluding with December 1989.