1901
| Winter | Supervises construction of the Edison Portland Cement Company works at Stewartsville, New Jersey, using some equipment from the nearby New Jersey and Pennsylvania Concentrating Works. |
| Feb 15 | Authorizes Herman E. Dick to negotiate abroad for the formation of companies to manufacture and sell storage batteries. |
| mid Feb | Opens a motion picture studio at 41 East Twenty-first Street in Manhattan. |
| Feb 27 | Begins vacation with his family in Fort Myers, Florida, and visits his winter home, Seminole Lodge, for the first time since 1887. Thereafter, takes frequent winter vacations in Fort Myers. |
| May 14 | Receives threatening letters demanding $25,000 in gold, "or we will kidnap your child." Hires Pinkerton detectives and the plot is foiled. |
| May 27 | Organizes the Edison Storage Battery Company. |
| June | Advertises in mining publications for information on dry placer mines that might benefit from his gold ore separation process. |
| July 17 | Sells granted and pending battery patents to the Edison Storage Battery Company for $999,000 of its $1,000,000 issued stock. |
| July 26 | Begins a six-week tour of upstate New York and Canada. Visits Niagara Falls and the Pan-American Exposition in Buffalo with his family before traveling by ship across the Great Lakes to Sudbury, Ontario, with his wife Mina Miller Edison. |
1902
| Jan | Introduces "moulded" records commercially. |
| Apr 25 | The Dunderland Iron Ore Company, Ltd., is organized by the Edison Ore Milling Syndicate, Ltd., to exploit Edison's ore processing technology in Norway. |
| May 2 | The Mining Exploration Company of New Jersey is incorporated to find and develop a supply of nickel for use in Edison's storage battery. |
| May 9 | Lord Kelvin (William Thomson) visits the West Orange laboratory. |
| May | Successfully conducts the first road tests of electric vehicles equipped with Edison storage batteries. |
| Aug | Begins commercial production of cement at his mill in Stewartsville. |
| Oct 23 | Nominally becomes a technical advisor to the Marconi Wireless Telegraph Company of America and assigns U.S. Pat. 465,971 to the company. |
| Dec 6 | Thomas A. Edison, Jr., sells the right to use his own name to the Thomas A. Edison, Jr., Chemical Company, makers of a patent-medical device called the "magno-electric vitalizer." |
1903
| Jan | Initiates production of his "E" type alkaline storage battery. |
| Mar 2 | An explosion at the Edison Portland Cement Company's coal grinding plant results in the death of eight workers, including chief engineer Edward A. Darling. |
| June 8 | Signs an agreement with his son Thomas A. Edison, Jr., whereby the younger Edison will not use his own name in any business enterprise in exchange for a weekly allowance of $35. |
| Sep–Oct | Newspapers report continuing labor unrest at the Edison works in Stewartsville and West Orange. |
| Nov 26 | Edison's attorney Judge Howard W. Hayes dies. Shortly afterwards, the Legal Department is established, with Frank L. Dyer as general counsel, to manage the legal concerns of Edison, his laboratory, and his companies. |
| Dec 10 | Writes to President Theodore Roosevelt in an effort to influence the U.S. Patent Office in its judgment on the relative merits of storage battery patents by Edison and Ernest Waldemar Jungner of Sweden. The Jungner patent is eventually declared invalid. |
| Dec | The Edison Manufacturing Company releases its hit film The Great Train Robbery, directed by Edwin S. Porter. |
1904
| Feb 10 | Dismisses chemist Martin A. Rosanoff, effective March 2, declaring that he is "the last foreigner in the chemical line that I shall hire. I prefer bright young Americans." |
| Apr | The Edison Manufacturing Company crew films re-enactments of the Russo-Japanese war for exhibition in the United States. |
| Sep 30 | Authorizes longtime associate Sigmund Bergmann to organize a corporation for the manufacture of storage batteries in Germany; nominally becomes a director of the Deutsche Edison Akkumulatoren Gesellschaft in April 1905. |
| Oct 2 | Laboratory employee Clarence M. Dally dies as the result of radiation burns sustained during x-ray experiments. |
| Nov 1 | Suspends the manufacture of his alkaline storage battery in order to investigate the loss of electrical capacity and leaking cans. |
1905
| Jan 23 | Undergoes an ear operation to remove or drain a mastoidal abscess. |
| Winter | Forgoes his annual vacation in Florida because of work on the storage battery. |
| Mar 7 | J. P. Morgan, Jr., visits the laboratory to discuss Edison's improved storage battery and the formation of European companies for its manufacture. |
| Summer | Begins a series of experiments using perforated tubes holding nickel flake as the positive electrode in his storage batteries. Tests continue for a decade. |
| Sep | Sends form letters to telegraph operators across the United States seeking information about possible deposits of cobalt ore for use in his storage battery. |
1906
| Jan 25 | Wins a thirty-year lawsuit against Jay Gould's Atlantic & Pacific Telegraph Company for infringement of his automatic telegraph patents; receives only one dollar in damages. The decision is reversed on appeal by both parties in February 1911. |
| Feb 17 | Marie Louise Toohey Edison dies; Edison pays for the funeral and the obituary in the New York Herald. |
| Mar 26 | Buys a farm in Burlington, New Jersey, for his son Thomas A. Edison, Jr., who has recently been released from a sanitarium for the treatment of alcoholism. |
| May | Travels by car through North Carolina and other southern states prospecting for deposits of cobalt ore. |
| July 7 | Thomas A. Edison, Jr., marries Beatrice Heyzer Montgomery with whom he has been living under the assumed names of Burton and Beatrice Willard. |
| Oct | Conceives and announces a plan to develop molds whereby an entire house can be made of poured concrete. |
1907
| Feb 11 | Announces his intention to "give up the commercial end and work in my laboratory as a scientist." |
| Mar 5 | The U.S. Circuit Court of Appeals finds for Edison in Thomas A. Edison v. American Mutoscope & Biograph Company, affirming the validity of his reissued camera patent and increasing his control of American film production. |
| July | Transfers the production of motion pictures from the Manhattan studio to a newly constructed studio in the Bronx. |
| Sep 16 | The National Phonograph Company opens new offices in New York City at 10 Fifth Avenue, eight blocks south of its new recording studio in the Knickerbocker Building at Fifth Avenue and 16th Street. |
| Sep 27 | Sends instructions to shut down the Darby Mine in Ontario, Canada, because he has recently "dropped cobalt entirely" for his storage battery. |
1908
| Jan 8 | Signs a cross-licensing agreement with the North American Portland Cement Company for mutual use of important cement patents. |
| Jan 17 | The Edison Business Phonograph Company is incorporated. |
| Feb 17 | Private secretary John F. Randolph dies from a self-inflicted gunshot wound; he is succeeded by Harry F. Miller. |
| Feb 23 | Enters Manhattan Eye Ear & Throat Hospital and has two additional operations on his left ear; remains in hospital until March 10. |
| Mar | Charles L. Brasseur is hired to conduct experiments on color photography for motion pictures. |
| July 23 | Frank L. Dyer succeeds William E. Gilmore as Edison's chief executive officer. |
| Aug | Vacations with members of his family in the Pacific Northwest and Canadian Rockies. |
| Sep 1 | Takes control of the Lansden Company, a manufacturer of electric vehicles using Edison storage batteries. |
| Oct 1 | Introduces Amberol cylinder records. With approximately 200 threads each, these records increase playing time from two to four minutes. |
| Nov 16 | Frank L. Dyer hires a personal attendant for Edison to "safeguard him from possible cranks and other people who might annoy him." |
| Dec | Agreement achieved among motion picture manufacturers results in the organization of the Motion Picture Patents Company. |
1909
| Feb | Agrees to pay Jonas W. Aylsworth $25,000 and Walter H. Miller $10,000 if they can develop a 400-thread cylinder record. By previous agreement Aylsworth receives $35,000 and Miller $10,000 for their development of the 200-thread record. |
| Agrees to loan his son William Leslie Edison $150 to move to a house in the country. | |
| Apr | Receives a gold medal from the Royal Academy of Sciences in Sweden for his inventions in connection with the phonograph and the incandescent light. |
| June | Dictates personal reminiscences to Thomas C. Martin in order to provide additional material for Edison: His Life and Inventions (1910), the authorized biography prepared by Martin, Frank L. Dyer, and William H. Meadowcroft. |
| July 1 | Begins commercial manufacture of his new "A" type alkaline storage batteries. |
| Nov 10 | Dismisses motion picture director Edwin S. Porter. |
| Dec | Begins to develop a disc record and phonograph. |
1910
| Jan 1 | Edison's former associate and longtime friend Charles Batchelor dies. |
| Jan | Plans to establish an Engineering Department at the West Orange laboratory in order to centralize research and development for the numerous Edison companies. |
| Feb 11 | Jonas W. Aylsworth executes a patent application for Condensite, a phenolic resin that is subsequently used in Edison disc records. |
| Mar | A streetcar powered by Edison storage batteries begins operation on a crosstown line in New York City; the car is designed by Ralph H. Beach of the Federal Storage Battery Car Company with input from Edison. |
| John H. Powrie and Florence M. Warner are brought to West Orange to demonstrate and improve their method of color photography. Edison's previous arrangement with Charles L. Brasseur is discontinued. | |
| May | Exhibits a scale model of his poured concrete house at the Real Estate and Ideal Homes Exhibit at Madison Square Garden in New York City. Continues to receive international attention for his idea. |
| July 18 | Arranges with Miller Reese Hutchison to develop storage batteries for use in submarines. |
| Aug 26 | Demonstrates his kinetophone or "speaking pictures" to members of the press at the West Orange laboratory. |
| Sep 17 | Two electric vehicles equipped with Edison storage batteries leave New York on a promotional "ideal tour," ending with an ascent of Mt. Washington in New Hampshire. |
| Oct | Receives national attention after making statements to the press revealing his unorthodox religious beliefs, including his skepticism regarding the existence of an immortal soul. |
| Nov | Donates $25 toward a memorial to the Comte de Villiers de l'Isle-Adam, whose novel L'Eve Future (1886) includes a fictional Edison. |
