Series I consists of twelve mounted, captioned clippings from the January 31, 1932 New York Times, documenting the costumes of some notable attendees of the annual ball given by the Society of Beaux-Arts Architects in the Waldorf-Astoria Hotel. The 1932 ball was themed "A Pageant of Old New York and the First Inaugural Ball of the United States of America," and the several thousand elites attending wore ancestral costumes or reproductions dating from the colonial period through 1789.

Series II consists of a few portraits, a mounted clipping, and a copy photograph of a Harper's Weekly illustration of a scene at the controversial ball given by Bradley and Cornelia Sherman Martin at the Waldorf Hotel on February 10, 1897. Thrown during an economic depression, the event drew wide criticism from those who thought it an ostentatious display of wealth and excess. Chief among the critics was Reverend Dr. William S. Rainsford, rector of St. George's Protestant Episcopal Church, who sparked a frenzy in the press after criticizing the event on the pulpit and reportedly advising his parishioners not to attend. His statements spurred a public debate on the best use of wealth in society, with prominent public figures weighing in on the issue. The only vintage photograph of a guest in costume for this ball is a portrait of William Beekman by Gilbert Studios.

Series III consists of a group of sixteen photographs depicting attendees of an unidentified costume party labeled as being the Delmonico Ball of 1875. A variety of events were held at Delmonico's in 1875, the favorite restaurant and party venue of New York society in the Gilded Age. It is unclear which of the 1875 events the photographs in this collection depict. All photographs in this series were donated by Harold Seton. Included are a few mounted clippings from a later piece on the Harold Seton collection in the New York Herald Tribune in October 25, 1927.

Series IV consists of photographs depicting guests wearing antique costumes at an event given by Sarah Cooper Hewitt and her daughters, Sarah and Eleanor, in 1908. Mrs. Peter Cooper Hewitt is portrayed in a ball gown originally worn at the Prince of Wales Ball in 1860, and the Vicomte de Périgny is portrayed in wedding clothing dating from 1845. Also included with these photographs is a program for the French plays performed at this event in the Hewitt's private theater, including Guy de Maupassant's Histoire du Viéux Temps and Eugène Verconsin's Qûete à Domicile.

Series V comprises the bulk of the Costume Ball Collection; included are more than 150 portraits of attendees in costume for the fancy dress ball given by William K. and Alva Smith Vanderbilt in their newly built home at 600 Fifth Avenue on March 26, 1883. At the time, the ball was considered to be one of the most "lavish" in New York City's history. It featured guests dressed as courtiers, witches, royalty, godesses, and opera and nursery rhyme characters. Quadrilles were performed by guests dressed according to particular themes.

Included in this series are photographs of members of many of the elite families of New York, including the Astors, the Belmonts, and the Vanderbilts. Portraits in this series are almost exclusively the work of Mora, and include a variety of that studio's fanciful backdrops and props. The hostess, Alva Smith Vanderbilt (later Alva Belmont), is portrayed as a Venetian princess with a palatial background, surrounded by flying doves. Constance Rives Borland, dressed as a bee with protruding wings and antennae, is set against a convincing woodland background, and Grace Stebbins Chapin seems to dip her hand into a flower-strewn pond. Caroline Seward Endicott stands in a faux snowstorm with her hands tucked into a fur muff. Most of the photographs in this series bear brief identifications on the verso, and some also identify the costume or the quadrille in which the individual was featured.

Series VI contains photographs of people in costume for unidentified or unspecific parties or costume balls. It includes a folder of six group portraits, including one at Dr. Strong's Santitarium in Saratoga Springs, New York, dated 1896, and one undated portrait identified as a group at Sharon Springs, New York. Photographs are arranged alphabetically by sitter, with unidentified group portraits at the end of the series.