The collection is made up of approximately fifty percent loose material and fifty percent bound volumes (percentage estimated in shelf space). The loose material consists of documents, both routine business and legal, correspondence, reports, minutes, various types of financial business, and maps and blueprints. Many of the subsidiary companies represented in these papers are not present in the series of bound material, and this loose material is dated, on an average, earlier than the volumes. The Louisville, New Orleans and Texas Railway Company, which does not appear in the bound material, is involved in much of the earlier, loose material, and of particular interest are the business papers of the various railroad lines which consolidated to form this line. They consist of agreements and correspondence in particular, which presents a rather complete picture of the growth of railroads late in the nineteenth century. A railroad in Guatemala also illustrates an interesting aspect of the company's activity.

Of interest to Californians should be the rather extensive collection of business records and correspondence related to the Monterey Peninsula, i.e. the Hotel Del Monte, Pacific Grove real estate, and the street railway in San Francisco, the Geary Street Park and Ocean Railway Company.

A great bulk of this loose material consists of routine correspondence, which fills forty-five large boxes. It is dated from 1901 to 1927, and only the Pacific Improvement Company itself is directly involved, as all the letters are either directed to or written by the directors of that company. The letters are in regard to, however, the various businesses in which the Pacific Improvement Company was engaged, and they are most interesting because of the picture they present of the way routine business was conducted by the holding company itself.

Among the bound volumes, the subsidiary companies must completely represented are the Carbon Hill Coal Company of Washington State, the Ione Coal and Iron Company of California, the Geary Street Park and Ocean Railway Company, the Rocky Mountain Coal and Iron Company of Wyoming, the Oakland Water Front Company, and the Southern Development Company. Those represented to a lesser extent are the San Pedro Harbor Dock and Land Company, the Capay Valley Land Company, the Union Fuel Company, Monterey County Water Works, El Verano Villa Association and El Verano Improvement Association, the Sonoma Valley Improvement Company, and the various hotels in the Monterey area and Santa Barbara.

There are several other minor groups of books but those mentioned make up the bulk of this part of the collection. The types of volumes include: By-laws, minute books, stock journals and ledgers, general journals and ledgers, cash books, checkbooks, reports, trial balances, deed registers and voucher registers. In addition, there are twenty boxes of paid out contracts and deeds of the Pacific Improvement Company and a few subsidiaries.

Maps and blueprints are included at the end of the collection, following several unidentified volumes, and many show the exact extent of the holdings of the Pacific Improvement Company in certain areas at certain times, as well as the property owned by subsidiaries.

Although some of the groups of subsidiary company books are fragmentary, on the whole the collection is quite complete and would be a valuable source to anyone interested in early California business practices or in the activities of C.P. Huntington.