Ronald W. Clark (1916 - 1987) was a writer and biographer of Bertand Russell and Albert Einstein. Collection consists of two letters and one postcard of Ronald W. Clark to Mrs. E.C. Goodall thanking her for assistance.

Henry Clay Sr. (1777–1852) was an American lawyer, planter, and statesman. One letter written by Henry Clay accepting the nomination by the Whig convention to run for president, May 2, 1844.

The Carrollton Viaduct, located over Gwynns Falls near Carroll Park in Baltimore, Maryland, was the first stone masonry bridge built for railroad use in the United States. Collection consists of pages from the Citizens and Farmer's Almanac, July 1830, describing the Carrollton Viaduct.

George B. Coale (1819-1887) was an insurance executive in Baltimore. This collection consists of ten letters to George B. Coale ranging in date from 1832 to 1881.

Padraic Colum (1881-1972) was an Irish poet and playwright. Collection consists of one postcard (dated 1961) from Padraic Colum to Mabel Whiteley of Baltimore.

Peter Cooper (1791 – 1883) designed and built the first American steam locomotive. Collection contains one letter of Peter Cooper to John H.B. Latrobe dated October 7, 1880, and one drawing of Cooper's steam engine.

Collection consists of a letter from Arthur L. Corrigan (December 14, 1901) to "My Lord Cardinal." It is a request for money after a theft in London.

Edwin Charles Cort received his M.D. from Johns Hopkins University in 1907 and was a medical missionary in Siam (Thailand) from 1908 intil 1949. This collection consists of an essay entitled "Thirty Years of Medical Practice in Siam" from approximately 1948.

James Croll (1821-1890) was a Scottish geologist and climatologist. This collection consists of one letter of James Croll to Henry Sidgwick, May 12, 1883, asking for Sidgwick's opinion of an article.

Thomas S. Cullen was a graduate of and professor at the Johns Hopkins School of Medicine in the early 20th century. This collection consists of three letters of Thomas S. Cullen to members of the Johns Hopkins administration written in 1926, 1945, and 1949.

Edgar Allan Poe (1809-1849) was an American poet and story writer. The collection consists of a bound reprint of "A Notice of William Cullen Bryant" by Poe, which appeared in Burton's Gentleman's Magazine and American Monthly Review, IV, 203-205, dated May, 1840.

The collection consists of a poem, "Maryland," written by a Mrs. Lawson, most likely during the Civil War. The poem was intended as a satirical response to the pro-Southern lyrics of "Maryland, My Maryland," written by James R. Randall.