Brooks D. Simpson, "Creswell, John Angel James," American National Biography Online, February 2000, http://www.anb.org/articles/04/04-00280.html.
Originally a Whig, when the party broke up Creswell shifted allegiances to the Democratic party for a short while and in 1856 was a delegate to its presidential nominating convention. In the secession winter of 1860-1861, he declared for the Union, and as a member of the House of Delegates, he served to keep Maryland from seceding in 1861. The following year he was appointed assistant adjutant general for the state. In the fall of 1862 he won election as a Republican to Congress, beating incumbent John W. Crisfield. Creswell sided with the Radical Republicans in Maryland as an ally of Henry Winter Davis and played an important role in securing passage of emancipation in that state in 1864. That year he lost his bid for reelection. He served out Thomas Hicks's term in the U.S. Senate starting in 1865 but failed to secure election in his own right in 1867. Supporting congressional Reconstruction measures, he advocated the impeachment of President Andrew Johnson. In 1864 and 1868 he served as a delegate to the Republican presidential nominating conventions.