In 1921, Mary Dana-Hicks Prang, Louis Prang's widow, donated the publisher proofs to NYPL (see her letter of donation, Digital ID: 482882, along with a company history and image index, Digital ID: 482883, in the first scrapbook); the group of advertising cards joined the collection in 1927.
Louis Prang (1824-1909) was one of the most prolific and influential print publishers of the 19th-century. His Boston-based firm specialized in chromolithography, a technique of printing multi-color lithographs that eliminated the need for labor- and time- intensive hand-coloring. His output ranged from reproductions of paintings and maps to album cards, business cards and greeting cards, and he is credited with being the first publisher of Christmas cards. These publications feature typically Victorian subjects such as flora and fauna, animals, angels and cupids, and children.
Freman, Larry. Louis Prang; Color Lithographer; Giant of a Man. 
Holzer, Harold, ed. Prang's Civil War Pictures: The Complete Battle Chromos of Louis Prang with the Full "Descriptive Texts." 
McClinton, Katharine Morrison. The Chromolithographs of Louis Prang. 
Marzio, Peter. The Democratic Art: Pictures for a 19th-Century America.