The extensive collection of papers preserved in the archives of the Thomas Edison National Historical Park (TENHP) —approximately 5 million pages in all—is the product of Thomas Alva Edison's sixty-year career as inventor, manufacturer, and businessman. Before the advent of the Thomas A. Edison Papers project, the sheer size and organizational complexity of the archive deterred researchers from delving extensively into its wealth of documentary resources. With the publication of the microfilm, book, and digital editions, these historically significant papers are now readily available to scholars and other researchers. Because the arrangement of the documents in the microfilm and digital editions parallels the organizational structure of the archives, it is helpful to understand how the records of Edison's laboratories and companies were generated during his own lifetime and how the archivists entrusted with their guardianship have subsequently treated them.

Although Edison began his career as a professional inventor in 1869, he did not attempt to keep systematic records of his experiments until 1871. A pocket notebook from October 1870, in which he entered specifications and drawings for printing telegraph apparatus, contains the concluding note: "all new inventions I will here after keep a full record." This determination to keep a full record of inventive activity in anticipation of patent and contractual litigation soon led to the creation of more than a dozen technical notebooks of varying sizes and shapes, many of them containing beautiful drawings. Frequently, the entries in these notebooks were dated, signed, and witnessed. Edison and his associates also used numerous loose pieces of paper to record ideas in the midst of research. When Edison moved from Newark to Menlo Park in 1876, many of the unbound notes and drawings were lost. Perhaps as a result of the difficulty experienced in keeping these pieces of paper together, many of them were subsequently pasted into scrapbooks. Edison did not, however, adopt a systematic method for doing this. Many unbound notes and drawings were not put into the scrapbooks, and related materials within the books were often widely separated.

Edison and his associates used ledger volumes, pocket notebooks, and unbound scraps of paper on an irregular basis throughout the inventor's career. In 1877, however, Edison instituted a more regular practice for note keeping that, with some refinements, continued throughout his life. At first Edison used 9" × 11" softcover tablets, whose sheets tore away from the top edge. Only a few of these notebooks were retained in their original condition. The majority were taken apart and, together with material on other loose pieces of paper, were organized according to the specific invention to which they related. By the fall of 1878, the number of notes and drawings from Edison's work on the electric light had grown so large that he adopted a standard-size hardbound notebook that would remain intact as a permanent record. Like the tablets, the notebooks were placed around the laboratory and often recorded the work of more than one experimenter. The first of these notebooks dates from November 1878. Edison and his associates continued to use such notebooks for recording experimental work at Menlo Park and at Edison's later laboratories. The TENHP archives has over 3,000 such notebooks, each measuring 6" × 9" and containing approximately 280 pages.

Not all of Edison's notebooks are experimental in nature. Some of the earliest books contain accounting records, and sometimes experimental and financial material are indiscriminately mixed together in the same book. At his West Orange laboratory, Edison used some of the standard size books, as well as numerous pocket notebooks, to record ideas about the operations of his factories and businesses. In addition, there are several hundred notebooks containing evaluations of phonograph recordings and tests of storage batteries.

Although Edison seems to have retained most of his technical notes and drawings, some of them were lost or misplaced after their introduction as exhibits in civil court and patent interference cases. Not infrequently, the facsimiles and transcripts found in the printed record of these cases constitute the only surviving record of these documents. This is well illustrated in the case of the many drawings entered into evidence in the telephone interference proceedings in 1880.

The large collection of patent records at the TENHP constitutes another important source for understanding Edison's activities. In the early 1870s, Edison began to retain correspondence from his patent attorneys and from the U.S. Patent Office. In addition, rough drafts and finished copies of his patent applications were occasionally entered into the notebooks. However, Edison did not initially keep comprehensive files of his applications or of the correspondence between his attorneys and the Patent Office examiners. Thus, the major body of documentation on Edison's early patents is in the Patent Office files, located in Record Group 241 at the National Archives and Records Service. Around the turn of the century, Edison established his own patent department, and its extensive collection of patent folio files is preserved in the TENHP archives.

Another important source of information about Edison's technical work is his scrapbooks. Edison and his associates prepared scrapbooks from an early date and included both unbound technical notes and articles clipped from newspapers and journals. As in the case of the notebooks, they initially employed a variety of different types of books and later instituted more systematic record-keeping procedures. In 1878 or 1879, William Carman and Francis Upton began using a standard-size scrapbook to keep a record of the growing number of articles about Edison and the technologies in which he was involved. Approximately 150 of these Menlo Park scrapbooks are still extant, and there are indications that the series may once have comprised over 200 books. The first 57 scrapbooks are numbered and indexed, and they deal primarily with technical subjects. The other volumes are largely concerned with scientific matters. After the move to West Orange, Edison and his associates continued to keep scrapbooks, but most post–1887 scrapbooks in the TENHP archives are either photo albums or collections of published interviews with Edison.

In addition to generating an enormous quantity of technical material, Edison also maintained extensive correspondence files. Prior to 1878 Edison had no secretary, although various individuals working at the laboratory and shops had some responsibility for filing correspondence. The fame that the phonograph brought to Edison in 1878 resulted in a substantial increase in the volume of his mail. Edison was deluged with unsolicited fan mail and letters seeking advice or requesting information about his inventions. As a result, he hired Stockton L. Griffin, an old friend from his days as a telegrapher, as his secretary. Griffin developed a system of filing correspondence by subject or, in the case of frequent correspondents, by the name of the individual. This system continued, with some modifications, to the end of Edison's life.

Edison did not preserve copies of his outgoing letters until 1875, when he began using letterpress copies to record outgoing correspondence. The earliest letterpress copybooks relate primarily to routine business matters. However, the researcher may discern the nature of the reply to many other incoming letters from the notes written in their margins by Edison and his secretaries. After 1881 Edison became more systematic in preserving copies of outgoing correspondence, but he and his secretaries continued the practice of writing marginal comments on incoming letters.

The letterbooks provided a less than ideal means of recording outgoing correspondence. The letterpress copies were made by wetting the leaf of the copying paper and then placing the original letter on the leaf and blotting it. This process often produced bad copies as a result of bleedthrough, faint ink, and smearing or spreading of the ink. Moreover, the thin tissue pages were easily susceptible to wrinkling, fraying, and tearing. These problems are more common in the early letterbooks..

Edison was continually establishing companies to manufacture and market his inventions, and the majority of the documents in the TENHP archives deal with his business operations. In addition to the correspondence, Edison and his associates generated a substantial number of legal records such as agreements, patent assignments, powers of attorney, stock certificates, mortgages, deeds, and insurance policies. Edison's companies also kept extensive financial records, including bound account books, draft account sheets and trial balances, bills and receipts, payroll and time records, and lists of tools and supplies. At Edison's earliest manufactories in Newark, different types of accounts were often mixed in the same ledger, and some books even contained entries for several different companies. Later, at Menlo Park and West Orange, Edison employed professional bookkeepers, who systematized the accounting records.

By the twentieth century, Edison had built in New Jersey a small industrial empire that culminated in 1911 in the organization of Thomas A. Edison, Inc. As a result of the increasing number, scale, and bureaucratization of his businesses, the amount of documentation for Edison's twentieth-century activities is much greater than that for the nineteenth century, and the character of the material is more heavily oriented toward business records. The laboratory continued to play an important role in Edison's career, but it became merely one part of a large business organization. Much of its work was directly related to improvements for the various manufacturing companies. Because of the increasing size and organizational complexity of the Edison companies, many new types of business records were generated. Included among these were (1) interoffice communications and memoranda; (2) legal files maintained by key Edison associates such as Harry F. Miller and Richard W. Kellow and by the company's legal department; (3) advertising materials for the phonograph, storage battery, and other Edison products; (4) folios for patents assigned to the various Edison companies; (5) manufacturing records such as inspection reports, blueprints, and test runs; and (6) labor records for a vastly expanded work force.

Even before his move to West Orange in 1887, Edison had taken steps to preserve the records of his earlier activities in Newark, Menlo Park, and New York. Sometime before 1887, the correspondence, financial papers, and other unbound laboratory and business records were gathered into small packages, labeled, and placed in eighteen large wooden packing cases. These were subsequently moved to West Orange and placed in Edison's library in the main laboratory building. In 1912 Edison constructed a fireproof concrete vault near the laboratory for the safekeeping of his early notebooks, important legal papers, and other valuable documents.

Edison and his secretaries did not adopt a systematic plan for storing and preserving the ever-increasing quantity of correspondence, business records, and other papers dating from the period after 1887. Some of the documents for the early West Orange years were later placed in the wooden packing cases with the pre–West Orange material, while others were either left on shelves and floors in the galleries of the library or were packed into crates and boxes to be stored in the numerous library cabinets. As the volume of material increased, other rooms on the second and third floors of the laboratory were pressed into service as storage areas. In 1918 a Vault Service Department was created within Thomas A. Edison, Inc. to identify and store obsolete business records generated by the department heads and other company officials.

Not until late in the 1920s did Edison or his associates appreciate the need for a systematic appraisal of a body of records that now totaled several million pages. In the summer of 1928—three years before Edison's death—the company hired Mary Childs Nerney to head a new Historical Research Department, and she prepared a detailed inventory of the large packing cases containing Edison's earliest business records. Although much of this material had originally been labeled and packaged, Nerney found that, over the years, the papers had "been combed many times and many of them thrown back helter skelter." In the process, the contents of different packets had been mixed, and many papers were lying loose in the boxes. Before leaving the company in 1930, she organized a few of the most important documents according to subject categories established by Edison's early secretaries and placed them in metal file drawers.

The organization of the Document File, as this collection was called, continued under the leadership of Norman R. Speiden, who served as director of the Historical Research Department and curator of the Edison laboratory from 1935 until 1970. Before the work was interrupted by World War II, the papers for the years through 1882 had been identified, organized by subjects within each year, and indexed on 3" × 5" cards. The processing of the documents resumed in 1948 when Kathleen L. Oliver (later McGuirk) became archivist of the collection. By the time of McGuirk's retirement in 1971, much of the correspondence and other unbound material through 1912 had been integrated into the Document File.

At the same time that Speiden and his associates were arranging the unbound documents, they were also collecting, organizing, and indexing the many hundreds of notebooks scattered throughout the laboratory and factory complex. Each of the standard-size notebooks was assigned a six-digit "N-number," and its contents were summarized on a 3"× 5" index card. As voluminous numbers of notebooks, accounting records, legal papers, letterbooks, and other documents were integrated into the collection, the existing buildings could no longer provide adequate storage. By the spring of 1942 the company completed construction of a spacious, air-conditioned underground vault.

The years following World War II witnessed the culmination of long-standing plans to turn the laboratory into a museum and to make its collections of documents and artifacts more accessible to researchers. In June 1946 the Thomas Alva Edison Foundation was incorporated as a nonprofit organization, and on February 11, 1948—the 101st anniversary of Edison's birth—the Foundation opened the library and laboratory to the public and assumed responsibility for the operation of the museum and the administration of its collections. In September 1955, after twenty months of negotiations with Charles Edison and other officials of Thomas A. Edison, Inc., the National Park Service made a formal offer to take over custodianship of the Edison laboratory complex. President Dwight D. Eisenhower officially designated the laboratory buildings and 1½ acres of land surrounding them as the Edison Laboratory National Monument on July 14, 1956, and six years later the laboratory and Glenmont, Edison's home in nearby Llewellyn Park, were collectively designated as the Edison National Historic Site (renamed the Thomas Edison National Historical Park in 2009).

The contents of the library and the underground vault were officially donated to the National Park Service in late 1957. However, the McGraw-Edison Company, the successor to Thomas A. Edison, Inc., still retained ownership and possession of more than a million pages of business records generated prior to Edison's death in 1931. Over a period of fifteen years, these records were gradually removed from the company's vaults and transferred to the custody of the National Park Service. The transfer continued until 1972, when the company moved from West Orange. In addition to these company records, the TENHP also received donations of important papers from the descendants of Charles Batchelor, Francis R. Upton, and other Edison associates.

These massive acquisitions put a severe strain on the resources of the archives staff, and much of this new material remained inaccessible to researchers. Moreover, despite efforts by Nerney and her successors to remove the manuscripts housed in the library and in other rooms within the laboratory, an estimated 200,000 pages of documents remained in these areas, many of them stored in the same boxes and crates into which they had been placed by Edison's secretaries.

During the 1960s and 1970s, the TENHP staff made considerable progress in organizing these materials and making them available to researchers. More than one million pages of account books and other business records were removed from their packing cases and stored in two above–ground fireproof vaults. The contents of hundreds of file boxes maintained by Edison's private secretary, William H. Meadowcroft, during the years 1913–1931 were also examined, and the processing of the most historically significant materials into the Document File was begun. However, approximately 450,000 pages of correspondence, interoffice communications, and other material from 1913–1931 remained in their original file boxes, forming an important adjunct to the Document File. In recent years, most of these unprocessed documents have been integrated into the Document File, which has been renamed the Edison General File. Since 1979 the staff of the Thomas A. Edison Papers has worked closely with the archives staff to improve the organization of this record group and other collections selected for publication.

The publication of the microfilm and digital editions has now made this core of Edison's papers available to scholars and other researchers. Equally important, the editions contain references to related material not selected for inclusion and thus serve as an important entree into the larger collection. Through painstaking transcription, careful annotation, and other editorial additions, the book edition is revealing the depth, breadth, and complexity of Edison's work with unprecedented detail. Plans are now underway to link the transcribed documents in the book edition with their images in the image edition, allowing users to examine the original documents more easily, quickly, and thoroughly than ever before possible.