According to the Forney Museum website, the 0-4-4 boiler forward, also capable of running 4-4-0 cab forward, was an early popular elevated and commuter rail engine in the U.S. This type steam locomotive was patented by Matthias Nace Forney, 1835-1908. Forney worked for the Illinois Central Railroad, 1861-64, when it was heavily involved in the shipping that gave the U.S. forces under Grant superiority in the Civil War, and in that period he patented his locomotive design for which he is known. Forney became an expert on steam locomotive theory, after 1870 working for the Railroad Gazette as an associate editor, and in 1874 first publishing his Catecism of the Locomotive: http://archive.org/details/cu31924031173549 .  This was the standard instruction book for locomotive engineers and mechanics for the last quarter of the 19th c. and into the 20th c., according to John H. White, Jr. in his History of the American Locomotive-- Its Development: 1830-1880 (Johns Hopkins, 1968; reprint Dover 1979), p. 490.  

This image is from the small-scale photo collection of Munson Paddock, 1886-1970, who in additon to being an illustrator and pioneer comics artist, was a collector of railroad images.  The library has collections that he put into storage in the 1950s when he retired and moved to harrisburg, PA.  By the mid 1970s his New York-stored materials were shipped to a relation in Lake Forest, IL, and through the facilitation of Anne Steinwedel (Mrs. Elliott) Donnelley (Hardy) Paddock's stored collections came to the Donnelley Library, now the Donnelley and Lee Library, Lake ofresyt College.  Materials that were at his Harrisburg home went to Strasbourg.  

The small, card-sized images were given numbers and listed by Whyte wheel type by Glenn Davis, Class of 1980, working as a Special Collections intern.  Early very low resolution images were created in the 1990s and linked to an electronic version of David's listing.  These images now are being upgraded in resolution and metadata added.