He is the oldest son of Fred Bernstein (1922-2001) and Marilyn [Berman] Bernstein (1927-2016); his siblings are the artist Linda A. Bernstein (1958-2004) and the engineer, technology specialist, musician, and expert on BMW Steven J. Bernstein (1962--). He was educated in the New York City public schools, graduating from Stuyvesant High School in 1973. He attended Amherst College, where he was graduated with a B.A. magna cum laude in 1977 in American Studies. While at Amherst, he was a research assistant to Henry Steele Commager. He was graduated from Harvard Law School with a J.D. in November 1980.
After three years practicing law, Bernstein left the legal profession to return to the study of history, doing graduate work at New York University. From 1983 to the present he has been a member of the New York University Legal History Colloquium, and he has been active in the writing of legal and constitutional history and in activities to promote the historical profession.
From 1984 to 1987 he was research curator for the Constitution Bicentennial Project of The New York Public Library, working with Kym S. Rice under the supervision of Richard B. Morris, Gouverneur Morris Professor of History Emeritus at Columbia University. Among the products of this project was Bernstein's first book, Are We to Be a Nation? The Making of the Constitution, published by Harvard University Press. From 1987 to 1990 Bernstein was historian on the staff of the New York City Commission on the Bicentennial of the U.S. Constitution, and from 1989 to 1990 he was research director of the New York State Commission on the Bicentennial of the Constitution.
In the spring of 1988 Bernstein was a visiting part-time lecturer in history at the Newark, New Jersey campus of Rutgers University. In 1991, he was named an adjunct assistant professor of law at New York Law School, where he has taught courses on American legal history and law and literature through 2014. In 2007 he was named Distinguished Adjunct Professor of Law. In 1997-1998 he also was the Daniel M. Lyons Visiting Professor of History at Brooklyn College of the City University of New York.
From 1997 to 2004 Bernstein was co-editor of book reviews for H-LAW, the listserv co-sponsored by H-NET (Humanities and Social Sciences Network On-Line) and the American Society for Legal HIstory. He is also a member of H-LAW's editorial board. For three years he served on the editorial board of Law and Social Inquiry, the journal of the American Bar Foundation. In 2004 he was elected to the board of directors of the American Society for Legal History for a three-year term (2004-2007); in 2011, he was elected for a second term as a director of the society, which expired in 2014.
In the fall semester of 2011, Bernstein joined the Skadden, Arps Honors Program in Legal Studies at the City College of New York as an adjunct professor of political science. In the fall semester, he taught American Constitutional Development; in the spring semester of 2012 he taught Early American Political Development. In the fall semester of 2012 he again taught Early American Political Development and a section of the one-semester survey course on American history; in the spring semester of 2013 he taught two sections of the survey course, and a political science course on the American judiciary. His repertoire of courses now includes courses on the American judiciary, the U.S. Congress, and the American presidency; American Political Thought; African American Political Thought; and Early American Political Development. Beginning in the fall 2015 semester, he was named a full-time lecturer in law and political science teaching classes like "The Presidency".
In 1993, Bernstein changed his byline from Richard B. Bernstein to R. B. Bernstein to avoid confusion with the several other Richard Bernsteins active in journalism and law.
In November 2002, in addition to his scholarly activities, Bernstein became director of online operations at Heights Books, Inc., a used-bookstore in Brooklyn. He ended his connection with Heights Books when the business closed at the end of February 2011.
Among the products of the New York Public Library's Constitution Bicentennial Project was Bernstein's first book, Are We to Be a Nation? The Making of the Constitution, published by Harvard University Press. Following Are We to Be a Nation?, Bernstein published Amending America: If We Love the Constitution So Much, Why Do We Keep Trying to Change It?, a history of the U.S. Constitution's amending process and the successful and unsuccessful attempts to amend the Constitution from 1789 through the early 1990s; Thomas Jefferson and Bolling v. Bolling: Law and the Legal Profession in Pre-Revolutionary America, coedited with Barbara Wilcie Kern and Bernard Schwartz (the full text, transcribed with scholarly annotations, of the pleadings and arguments of a complicated 1770 lawsuit about wills and bequests that pitted George Wythe against Thomas Jefferson); and Thomas Jefferson, published in 2003. Gordon S. Wood, reviewing Bernstein's Thomas Jefferson for The New York Times Book Review, called the book "the best short biography of Jefferson ever written."
Bernstein also co-edited several books with Professor Stephen L. Schechter of Russell Sage College, including Well Begun: Chronicles of the Early National Period (1989), New York and the Union: Contributions to the American Constitution Experience (1990), New York and the Bicentennial (1990), and Contexts of the Bill of Rights (1990). Roots of the Republic: American Founding Documents Interpreted, coedited with Schechter and Donald S. Lutz of the University of Houston, also appeared in 1990.
Bernstein published The Founding Fathers Reconsidered (Oxford University Press, 2009) in 2009, which on February 19, 2010, was named one of three finalists for the 2010 George Washington Book Prize sponsored by Washington College in partnership with the Gilder Lehrman Institute of American History and George Washington's Mount Vernon. In 2015, he published The Founding Fathers: A Very Short Introduction (Oxford University Press, 2015). In 2016 He published the edited volume An Expression of the American Mind: Selected Writings of Thomas Jefferson (Folio Society). His books-in-progress include a concise life of John Adams modeled on his 2003 biography of Thomas Jefferson; a study of the First Congress as an experiment in government; and an examination of the place of scientific ideas and technological developments in American constitutional history.