Pro Tem: Presidents pro tempore of the United States Senate since 1789, traces the development of the position in four brief essays which are accompanied by biographical profiles of all presidents pro tempore (1789-2010) including images for nearly all individuals who have served in this important position. The stories demonstrate the evolving nature of the Senate as well as its attempt to maintain many of its 18th-century ideals.

This work contains biographies of over 12,000 individuals. The origins of the Biographical Directory go back to 1859, when Charles Lanman, an author and former secretary to Senator Daniel Webster, assembled the first collection of biographies of former and sitting members for his "Directory of Congress." With the creation of the Senate Historical Office in 1975 and the House Office of the Bicentennial in 1983, professional historians assumed the responsibility for revising and updating the Directory. The print edition covers all members of Congress from 1774-2005. The online edition is a searchable database and is updated at each change of Congress or change in membership. To learn more about this publication see, Biographical Directory of the United States Congress.

Holding the least understood, most ridiculed, and most often ignored constitutional office in the federal government, American vice presidents have included some remarkable individuals. Vice Presidents of the United States, 1789-1993 provides an overview of the constitutional origins of the position of vice president, and examines how the position has changed throughout U.S. history. Also found within the publication is a closer examination of the distinguished individuals who held the title of Vice President of the United States. This publication is available online with up-to-date content in the Art & History section under "Officers & Staff."

Compiled by Senate historians, Senators of the United States: A Historical Bibliography lists scholarly works about U.S. senators. Bibliographies for all U.S. senators can be found in the online Biographical Directory of the U.S. Congress under the menu option "Bibliography."