These records deal with the discovery of the dinosaur Diplodocus carnegii in Wyoming in 1899, its shipment to the Carnegie Museum in Pittsburgh and the subsequent creation and installation of casts of the dinosaur in natural history museums in Europe, South American and Mexico. The material consists of correspondence, field reports, financial records, mining claims, photographs and newspaper clippings. The dinosaur remains were reproduced for several countries at the request of Andrew Carnegie who funded the project and for whom the dinosaur was named.

The records exist in 22 file folders in two Hollinger boxes in a metal cabinet.  They date from 1899 to 1903, have a four year gap and resume in 1907 through 1931.

The records are mostly correspondence pertaining to the Diplodocus carnegii with important and relevant correspondence of the museum's second director, William J. Holland, who turned the museum into one of the most important institutions of its kind.