Series I. Individual and Family Portraits holds images of men and women, some with family members, photographed primarily in one of the Pach Brothers studios. The sitters are nearly all Americans, and are a mix of nationally prominent personalities and socially prominent New Yorkers. The portraits are predominantly 10 x 8 inch black and white photographs affixed to 12 x 8.5 inch tan one-ply boards on which the patron's name and life dates have been typed below the image. A second format in the collection is what Pach Brothers, in their 1947 gift, described as "Large-Size Portraits," or unmounted 12 x 9 inch gelatin silver prints.

In addition, there are random pre-1900 albumen prints present in various sizes and formats. Several sepia-toned albumen group portraits of Ulysses Grant and George W. Childs with their family and friends were taken at their Long Branch, New Jersey, homes in the 1870s. Other individual portraits, such those of as Frederick Barnard (who was provost of Columbia University from 1864 to 1884 and died in 1889), Luke Blackburn, and William Henry Crane were certainly made in the early 1880s. Many of the albumen prints are in a 3.5 x 2.75 inch oval format mounted on the same labeled tan boards (Antoinette Carter Hughes is one example) described above. There are also a few photographs mounted on Pach's standard commercially-produced printed cabinet card boards, such as the portraits of United States Attorney General Henry Wise, banker Giovanni Morosini and his daughter Giulia, and the noted Lilliputian boxer Ebert P. Zink. There is one example of a nineteenth-century Pach Brothers stereograph in the collection, a portrait of Nellie Grant Sartoris, the popular daughter of President Grant.

The collection also includes copy prints, showing that the Pach studios also turned out second-generation images at the request of their patrons. Photographs include a group portrait of Rutherford Hayes's presidential cabinet made from a print, portraits of Admiral David Farragut and James Garfield, and a photograph of an engraved portrait of Abraham Lincoln. There are two photographs of George Dewey, one a nineteenth-century albumen print and one a later silver gelatin print made from the same negative. Two other photographs have format notes of interest to show Pach Brothers techniques. Explorer Robert E. Peary's portrait has an arc of light through the right side of the image revealing that it was printed from broken glass negative, and a group portrait of the Stokes family includes thirty two family members, some of whom were added to the photograph by the composite technique. Most of the photographs are not signed, but many (for instance, Seth Low) have the Pach name blind stamped in the lower right corner of the image.

The photographs in this collection were nearly all taken in one of the Pach Brothers studios, and are generally head-and-shoulders portraits of seated patrons. However, the verso of Ebert Zink's cabinet card portrait carries a printed advertisement for the firm that states their willingness to photograph "At your own Home when necessary," and a few portraits made at other sites can be found. For example, Ethel Barrymore was photographed in bed cradling her first child, and Madam Nijinski posed in front of a fireplace over which hung photographs of dancer Vaselev Nijinski. David Belasco, Andrew Carnegie, Virginia Gildersleeve, Luigi Palma di Cesnola, and Walter Lippman were photographed at their office desks, Charles Addison Miller in his office, and Mark Twain in his writing studio. Off-site occupation-related images are here as well: Thomas Lipton stood shipboard on a catwalk. William Crane Carl, in his robes, played a large pipe organ in his portrait, lyricist Leo Ditrichstein sat at the keyboard of a grand piano for his, and the duo Van & Schenk posed with two grand pianos. Artist Robert Henri stood holding paintbrushes with an unfinished portrait on his easel and sculptor John Quincy Adams Ward posed with a maquette. Illustrator Otto Soglow sat a drawing board working on a sketch of his famous character "The Little King," and Ham Fisher posed casually with one of his cartoons. Thomas Edison was photographed twice, including one portrait made in his laboratory office beside a cylinder-recording machine.

Political figures include every American president from Ulysses S. Grant through Franklin D. Roosevelt as well as several New York State governors and New York City mayors. There are a just few portraits of foreign officials, including Heinrich Bruning, chancellor of Germany, French diplomat Compte de Paris, Persian Consul General Haigazoun H. Topakyan, and Wu ting-Fang, Envoy Extraordinary and Minister Plenipotentiary of China to the United States. Theatre and film personalities are present, such as Maude Adams, Charles Chaplin, Douglas Fairbanks, Joseph Jefferson, Jean Harlow, Richard Mansfield (represented by three portraits, two of which are in costume) and Edna May. Literary and cultural figures include Sinclair Lewis, Richard Watson Gilder, Oscar Hammerstein, Irving Ramsey Wiles, Bennett Cerf, and Igor Cassini (known as Cholly Knickerbocker) among others.

The majority of the Pach Brothers' portraits are straightforward and formal in style and, though distinguished, somewhat unremarkable. There are occasional instances of overt glamour. Catherine Calvert was draped in furs and jewels, and Frieda Hempel, swathed in diamonds, posed with her little dog. Gertrude Lawrence chose pearls and feathers to accessorize her portrait, and Rita Weiman donned very stylish drop earrings laden with pearls. Raymond Hitchcock was dapper in his striped trousers, bowler hat and silver-handled cane. The Pach portraitists were, however, certainly capable of producing artistic work as demonstrated by perhaps the most dramatic and arresting image in the collection: a pensive portrait of actress Julia Marlowe. She was lit from above to accentuate the ethereal mass of her upswept hair and splendid fur-edged cape, and to reflect just the right light back into her upturned eyes.

However, most of the Pach patrons found in this collection are American businessmen, with a smattering of men of religion, military officers, jurists, and cultural figures; they are largely shown attired in suits, daywear, or evening clothes. Prominent New York families are well represented, and the collection includes portraits of Astor, Goelet, Guggenheim, Havemeyer, Roosevelt, Sloan, and Vanderbilt men among others.

The Pach Brothers Portrait Photograph Collection holds a single image for each sitter unless indicated by a number in parentheses following a name in the box and folder list. Some patrons returned to sit for the Pach Brothers over the years: Edward Finch had three separate portraits taken throughout his career, and Virginia Gildersleeve was photographed at two stages of her administrative career, both times at the same desk in the same office. Charles Evans Hughes' second portrait was taken much later in his life when his hair and beard had turned white. Portraits of children or youths in the collection are few, and are of sitters who made repeat visits to the Pach studios. J. Schuyler Casey was photographed three times, once at age one and again as a student at Mount Pleasant Academy. John J. Pershing has four portraits, two made while he was a cadet at the United States Military Academy at West Point (from which he graduated in 1886) and two taken later in his military career. Theodore Roosevelt is pictured six times over the course of his life, the last time posed holding his grandson.

The photographs in the Pach Brothers Portrait Photograph Collection are filed alphabetically by sitter surname. Names are listed in accordance with established Library of Congress name authority records, and cross references have been added to any which have been moved when the collection was processed (for instance, Samuel Clemens is now filed under Twain, and Dorothy Dix is filed as Elizabeth Gilmer). Oversize images are filed in Box 9, with cross-references in the Series I box list.

There is a single portrait of each each sitter unless a number follows after the name.

Series II. Oversize and Group Portraits contains oversize individual, family group, and group portraits of various people associated through corporate, government and social organizations. Corporate group portraits include the Kress, Singer, Sloan, and Woolworth companies, and the 1908 New York Giants baseball team. Government images are President Hayes and President McKinley with their cabinets, and the members of a Public Services Commission. Social groups are represented by a portrait of a fundraising committee for a World War I-era Allied Ball, and two images of the founders of Delta Upsilon fraternity.

Arranged in two subseries: Individuals and Family Groups; and Corporate Groups

Series III. Buildings holds photographs of street scenes that include portraits of buildings where the Pach Brothers had their studios in New Jersey and New York City; a glimpse of one of their office interiors can be seen in the brothers' group portrait in Box 6, Folder 50. This series also holds one photograph of Madison Square Garden and one of the Fifth Avenue Hotel, both in New York.