The collection consists of four series: correspondence, railroad-related material, other printed material, and photographs. Representative formats include paper records, brochures, newspaper clippings, bound volumes, maps, and photos. U.S. Military Railroads activities during the Civil War period (especially 1863-1864) and the Russian Grand Duke Alexis’s state visit to the United States in 1871-1872 are especially well documented.

Mr. Thomson’s correspondence between 1861 and 1864, much of which details the day-to-day administrative operations of the United States Military Railroads, may be of particular interest to researchers interested in the Civil War. Researchers interested in railway history should note that although railroad materials comprise their own series, much of Mr. Thomson’s correspondence also documents the administration of the U.S. Military Railroads. Most of the paper records in the Pennsylvania Railroad subseries deal with the Grand Duke Alexis’s visit, which was the largest official state visit by Russia to the United States to that time. The administrative history of the Pennsylvania Railroad itself is not particularly well documented in Mr. Thomson’s correspondence, but the collection does contain maps, books, publications, and other printed matter relating to the railroad.

The provenance of the collection, and how it came to the archives at Drexel University, is unclear. The correspondence, which consists of letters to and from Mr. Thomson, was clearly collected by him, and the printed matter and some of the railroad-related material were also presumably collected by Mr. Thomson. Other parts of the collection, however, such as the portion of the printed matter series that relates to Mr. Thomson’s death, are believed to have been collected by Mr. Thomson’s daughter, Anne.

Original order has been lost over time; arrangement of the collection has been imposed by the archivist. Correspondence is arranged chronologically to the year. Railroad-related material is divided into three subseries: one for the United States Military Railroads, one for the Pennsylvania Railroad, and one for other, unidentified, or general railroad material. The printed matter series contains subseries for materials relating to Mr. Thomson’s promotion to president, his death, and general printed matter. Some items, because of their large size or special storage requirements, have been physically separated from the rest of the series and are stored in oversized storage boxes.

Poor paper quality and improper storage over time have led to physical deterioration of some records. During processing, a number of newspaper clippings and telegrams were photocopied and the originals discarded because of their poor condition. Much of the correspondence and railroad material was folded for many years and is therefore fragile along the creases.