He joined the professional staff of the Library of Congress in 1871. He was eighteen years old, and only the second black American to work for the Library. Murray became the personal assistant to the Librarian of Congress, Ainsworth Rand Spofford at the age of nineteen.
By 1881 he had risen to become assistant librarian, a position he held for forty-one years.
Murray married educator Anna Jane Evans (1858 - 1955) on April 2, 1879, with whom he had seven children. The couple became a major force in the social and civic life of the District of Columbia.
African American writings
Murray began to compile a collection of books and pamphlets authored by African Americans at the request of Herbert Putnam, the successor to Spofford. The collection was to be an exhibition for the 1900 Paris Exposition on "Negro Authors".
In 1900 Murray published a list of the collections" holdings to date and appealed for additions to the list through donations.
Within several months, his list had grown to eleven hundred titles. The Library of Congress"s "Colored Authors" Collection" originated from his efforts. Now known as the "Daniel A. P. Murray Pamphlet Collection", it contains works dating from 1821 by such authors as Frederick Douglass, Booker T. Washington, Ida B. Wells-Barnett, Benjamin West. Arnett, and Alexander Crummell.
African American affairs
Murray was widely acknowledged as an authority on African-American concerns.
He was also a prolific author, and a frequent contributor to African American journals, in particular The Voice of the Negro. He was also well known for his writings on African American history, including his monumental but uncompleted Historical and Biographical Encyclopedia of the Colored Race.
Murray"s personal library of African American works was bequeathed to the Library of Congress upon his death March 31, 1925.
He was the first African-American member of the Washington Board of Trade, and he testified before the House of Representatives about Jim Crow laws and the migration of African-Americans from rural locations to urban areas. He was twice a delegate to the Republican National Convention and was a member of many other councils and organizations.