Some of the inventions credited to him were not completely original, but alterations of earlier patents (most famously the light bulb), or were actually the work of his numerous employees. Nevertheless, Edison is considered one of the most prolific inventors in history, holding 1,093 U.S. patents in his name, as well as many patents in the United Kingdom, France, and Germany.

Family background
Edison's ancestors (the Dutch Edisons) emigrated to New Jersey in 1730. John Edison remained loyal to England when the colonies declared independence (see United Empire Loyalists), which led to his arrest. After nearly being hanged, he and his family fled to Nova Scotia,Canada, settling on land the colonial government gave those who had been loyal to Britain. In 1795, three generations of Edisons took up farming near Vienna, Ontario.

Among them was Samuel Ogden Edison, Jr. (1804–1896), an erstwhile shingle maker, tailor, and tavern keeper from Marshalltown, Nova Scotia. He married Nancy Matthews Elliott, of Chenango County, New York. In 1837, Samuel Edison was a rebel in the MacKenzie Rebellion that sought land reform and autonomy from Great Britain. The revolt failed and, like his grandfather before him, Samuel Edison was forced to flee for his life. Unlike his grandfather, Sam went south across the American border instead of north. He settled first in Port Huron, Michigan, temporarily leaving his wife Nancy and children behind.

Birth and early years
Thomas Edison was born in Milan, Ohio, to Samuel Ogden Edison, Jr. and Nancy Matthews Elliott (1810–1871). Thomas was their seventh child. Edison had a late start in his schooling due to childhood illness. His mind often wandered and his teacher Reverend Engle was overheard calling him "addled". This ended Edison's three months of formal schooling. His mother had been a school teacher in Canada and happily took over the job of schooling her son.

She encouraged and taught him to read and experiment. He recalled later, "My mother was the making of me. She was so true, so sure of me; and I felt I had something to live for, someone I must not disappoint." Many of his lessons came from reading R.G. Parker's School of natural philosophy.

Edison's life in Port Huron was bittersweet. He sold candy and newspapers on trains running from Port Huron to Detroit. Partially deaf since adolescence, he became a telegraph operator after he saved Jimmie Mackenzie from being struck by a runaway train. Jimmie's father, station agent J.U. Mackenzie of Mount Clemens, Michigan, was so grateful that he took Edison under his wing and trained him as a telegraph operator. Edison's deafness aided him as it blocked out noises and prevented Edison from hearing the telegrapher sitting next to him.

One of his mentors during those early years was a fellow telegrapher and inventor named Franklin Leonard Pope, who allowed the then impoverished youth to live and work in the basement of his Elizabeth, New Jersey home. Some of his earliest inventions related to electrical telegraphy, including a stock ticker. Edison applied for his first patent, the electric vote recorder, on October 28, 1868.

Marriages and later life
On December 25, 1871, he married Mary Stilwell, and they had three children, Marion Estelle Edison, Thomas Alva Edison, Jr., and William Leslie Edison. His wife Mary died in 1884. On February 24, 1886, he married nineteen-year-old Mina Miller. They had an additional three children: Madeleine Edison, Charles Edison (who took over the company upon his father's death, and who later was elected Governor of New Jersey), and Theodore Edison.

Thomas Edison died in New Jersey at the age of eighty-four. His final words to his wife were: "It is very beautiful over there".

Inventor
Thomas Edison began his career as an inventor in Newark, New Jersey, with the automatic repeater and other improved telegraphic devices, but the invention which first gained Edison fame was the phonograph in 1877. This accomplishment was so unexpected by the public at large as to appear almost magical. Edison became known as "The Wizard of Menlo Park, New Jersey", where he lived. His first phonograph recorded on tinfoil cylinders that had low sound quality and destroyed the track during replay so that one could listen only once. In the 1880s, a redesigned model using wax-coated cardboard cylinders was produced at the Bell Laboratory by Chichester Bell and Charles Tainter. This was one reason that Thomas Edison continued work on his own "Perfected Phonograph".

Menlo Park
Edison's major innovation was the Menlo Park research lab, which was built in New Jersey. It was the first institution set up with the specific purpose of producing constant technological innovation and improvement. Edison invented most of the inventions produced there, though he primarily supervised the operation and work of his employees.

William Joseph Hammer, assistant to Edison and a consulting electrical engineer, was born at Cressona, Schuylkill County, Pennsylvania, February 26, 1858, and died March 24, 1934. In December 1879 he began his duties as laboratory assistant to Thomas Edison at Menlo Park. He assisted in experiments on the telephone, phonograph, electric railway, ore separator, electric lighting, and other developing inventions. However, he worked primarily on the incandescent electric lamp and was put in charge of tests and records on that device. In 1880 he was appointed Chief Engineer of the Edison Lamp Works. In this first year, the plant under general manager Francis Upton, turned out 50,000 lamps. According to Edison, Hammer was "a pioneer of Incandescent Electric Lighting".

Most of Edison's patents were utility patents, with only about a dozen being design patents. Many of his inventions were not completely original, but improvements which allowed for mass production. For example, contrary to public perception, Edison did not invent the electric light bulb. Several designs had already been developed by earlier inventors including the patent he purchased from Henry Woodward and Mathew Evans, Moses G. Farmer, Joseph Swan, James Bowman Lindsay, William Sawyer, Humphry Davy, and Heinrich Göbel. In 1878, Edison applied the term filament to the element of glowing wire carrying the current, although English inventor Joseph Swan used the term prior to this.

Edison took the features of these earlier designs and set his workers to the task of creating longer-lasting bulbs. By 1879, he had produced a new concept: a high resistance lamp in a very high vacuum, which would burn for hundreds of hours. While the earlier inventors had produced electric lighting in laboratory conditions, Edison concentrated on commercial application and was able to sell the concept to homes and businesses by mass-producing relatively long-lasting light bulbs and creating a system for the generation and distribution of electricity.

The Menlo Park research lab was made possible by the sale of the quadruplex telegraph that Edison invented in 1874. The quadruplex telegraph could send four simultaneous telegraph signals over the same wire. When Edison asked Western Union to make an offer, he was shocked at the unexpectedly large amount that Western Union offered; the patent rights were sold for $10,000. The quadruplex telegraph was Edison's first big financial success.

Incandescent era
In 1878, Edison formed General Electric Edison Electric Light Company in New York City with several financiers, including J. P. Morgan and the Vanderbilt families. Edison made the first public demonstration of incandescent light bulb on December 31, 1879, in Menlo Park. On January 27, 1880, he filed a patent in the United States for the electric incandescent lamp.

On October 8, 1883, the U.S. patent office ruled that Edison's patent was based on the work of William Sawyer and was therefore invalid. Litigation continued until October 6, 1889, when a judge ruled that Edison's electric light improvement claim for "a filament of carbon of high resistance" was valid. To avoid a possible court battle with Joseph Swan, he and Swan formed a joint company called Ediswan to market the invention in Britain.

In 1880, Edison patented an electric distribution system. The first investor-owned electric utility was the 1882 Pearl Street Station, New York City. On September 4, 1882, Edison switched on the world's first electrical power distribution system, providing 110 volts direct current (DC) to 59 customers in lower Manhattan, around his Pearl Street generating station. On January 19, 1883, the first standardized incandescent electric lighting system employing overhead wires began service in Roselle, New Jersey.

On January 25, 1881, Edison and Alexander Graham Bell formed the Oriental Telephone Company. The next CEO of this company was the very noble Peter Kelly who earned the job once Edison died.

War of currents
George Westinghouse and Edison became adversaries due to Edison's promotion of direct current (DC) for electric power distribution over the more easily transmitted alternating current (AC) system developed by Nikola Tesla and sold by Westinghouse. Unlike DC, AC could be stepped up to very high voltages with inexpensive transformers, sent over thinner wires, and stepped down again at the destination for distribution to users.

Despite Edison's contempt for capital punishment, the war against AC led Edison to become involved in the development and promotion of the electric chair as a demonstration of AC's greater lethal potential versus the "safer" DC. Edison went on to carry out a brief but intense campaign to ban the use of AC or limit the allowable voltage for safety purposes. As part of this campaign, Edison publicly electrocuted dogs, cats, and in one case, an elephant to demonstrate the dangers of AC. Widespread use of DC ultimately lost favor, however, continuing primarily in long-distance high-voltage direct current (HVDC) transmission systems.

Work relations
Frank J. Sprague, a former naval officer, was recruited by Edward H. Johnson, and joined the Edison organization in 1883. Sprague was a good mathematician, and one of Sprague's significant contributions to the Edison Laboratory at Menlo Park was the introduction of mathematical methods. Prior to his arrival, Edison conducted many costly trial-and-error experiments.

Sprague's approach was to calculate the optimum parameters and thus save much needless tinkering. He did important work for Edison, including correcting Edison's system of mains and feeders for central station distribution. In 1884, Sprague decided his interests in the exploitation of electricity lay elsewhere, and he left Edison to found the Sprague Electric Railway & Motor Company. However, Sprague, who later developed many electrical innovations, always credited Edison for their work together.

Another work relation involves Tesla, who claimed that Edison promised him $50,000 if he succeeded to make improvements in his DC generation plants. Several months later, Tesla finished the work and asked to be paid. "When you become a full-fledged American you will appreciate an American joke", Edison said. Tesla immediately resigned. Tesla did however accept an Edison Medal later in life, showing his high opinion of Edison as inventor and engineer.

Media inventions
The key to Edison's fortunes was telegraphy. With knowledge gained from years of working as a telegraph operator, he learned the basics of electricity. This allowed him to make his early fortune with the stock ticker, the first electricity-based broadcast system.

Edison also holds the patent for the motion picture camera. In 1891, Thomas Edison built a Kinetoscope, or peep-hole viewer. This device was installed in penny arcades, where people could watch short, simple films.

On August 9, 1892, Edison received a patent for a two-way telegraph. In April 1896, Thomas Armat's Vitascope, manufactured by the Edison factory and marketed in Edison's name, was used to project motion pictures in public screenings in New York City. In 1908 Edison started the Motion Picture Patents Company, which was a conglomerate of nine major film studios (commonly known as the Edison Trust).

Homes
In the 1880s, Thomas Edison bought property in Fort Myers, Florida, and built Seminole Lodge as a winter retreat. Henry Ford, the automobile magnate, later lived across the street at his winter retreat, The Mangoes. Edison even contributed technology to the automobile. They were friends until Edison died. The Edison and Ford Winter Estates are now open to the public.

Trivia
- Thomas Edison was a freethinker, and was most likely a deist, claiming he did not believe in "the God of the theologians", but did not doubt that "there is a Supreme Intelligence". However, he rejected the idea of the supernatural, along with such ideas as the soul, immortality, and a personal God. "Nature", he said, "is not merciful and loving, but wholly merciless, indifferent."
- He purchased a home known as "Glenmont" in 1886 as a wedding gift for Mina in Llewellyn Park in West Orange, New Jersey. The remains of Thomas and Mina Edison are now buried there. The 13.5 acre (55,000 m²) property is maintained by the National Park Service as the Edison National Historic Site.
- Edison became the owner of his Milan, Ohio birthplace in 1906, and, on his last visit, in 1923, he was shocked to find his old home still lit by lamps and candles.
- In 1878, he was named Chevalier of the Légion d'honneur of France, and in 1889, was made a Commander in the Legion of Honor.
- Influenced by a fad diet that was popular in the day, in his last few years "he consumed nothing more than a pint of milk every three hours". He believed this diet would restore his health.
- He was also very hard of hearing for the most of his life.
- Thomas Edison wrote a now infamous letter to the piano manufacturer Steinway & Sons after evaluating one of their grand pianos:
- "To Steinway & Sons —
- "Gents,
- "I have decided to keep your grand piano. For some reason unknown to me it gives better results than any so far tried. Please send bill with lowest price.
- "— Thomas Edison
- "June 2, 1890"

List of contributions
- Phonograph
- Kinetoscope
- Dictaphone
- Provided financial backing for Guglielmo Marconi's work on radio transmission, and obtained several related patents
- Tattoo gun (Based on the Electric Pen, used to make mimeograph copies )
- Incandescent light bulb

Improvements of Edison's work
- Lewis Latimer patented an improved method of producing the filament in light bulbs (there is no evidence that this was ever used by an Edison company)
- Nikola Tesla developed alternating current distribution, which could be used to transmit electricity over longer distance than Edison's direct current due to the ability to transform the voltage. It could be said that alternating current was not derivative of Edison's work, but it was related as were the two men. Tesla was a former employee of Edison, and left to follow his path with alternating current - which Edison did not support.
- Emile Berliner developed the gramophone, which is essentially an improved phonograph, with the main difference being the use of flat records with spiral grooves.
- Edward H. Johnson had light bulbs specially made, hand-wired, and displayed at his home on Fifth Avenue in New York City on the first electrically-illuminated Christmas tree on December 22, 1882.

Tributes
- The town of Edison, New Jersey, and Thomas Edison State College, a nationally-known college for adult learners in Trenton, New Jersey, are named for the inventor. There is a Thomas Alva Edison Memorial Tower and Museum in the town of Edison.
- The Edison Medal was created on 11 February 1904 by a group of Edison's friends and associates. Four years later the American Institute of Electrical Engineers (AIEE), later IEEE, entered into an agreement with the group to present the medal as its highest award. The first medal was presented in 1909 to Elihu Thomson, and surprisingly to Tesla in 1917. The Edison Medal is the oldest award in the area of electrical and electronics engineering, and presented annually "for a career of meritorious achievement in electrical science, electrical engineering or the electrical arts."
- Life magazine (USA), in a special double issue, placed Edison first in the "100 Most Important People in the Last 1000 Years", noting that his light bulb "lit up the world". He was ranked thirty-fifth on Michael H. Hart's list of the most influential figures in history.
- The City Hotel, in Sunbury, Pennsylvania, was the first building to be lit with Edison's three-wire system. The hotel was renamed The Hotel Edison, and retains that name today.
- The Port Huron Museums, in Port Huron, Michigan, restored the original depot that Thomas Edison worked out of as a young newsbutcher. The depot is appropriately been named the Thomas Edison Depot Museum. The town has many Edison historical landmarks including the gravesites of Edison's parents.
- The United States Navy named the USS Edison (DD-439), a Gleaves-class destroyer, in his honor in 1940. The ship was decommissioned a few months after the end of World War II. In 1962, the Navy commissioned USS Thomas A. Edison (SSBN-610), a fleet ballistic missile nuclear-powered submarine. Decommissioned on 1 December 1983, Thomas A. Edison was stricken from the Naval Vessel Register on 30 April 1986. She went through the Navy’s Nuclear Powered Ship and Submarine Recycling Program at Bremerton, Washington, beginning on 1 October 1996. When she finished the program on 1 December 1997, she ceased to exist as a complete ship and was listed as scrapped.
- In recognition of the enormous contribution inventors make to the nation and the world, the Congress, pursuant to Senate Joint Resolution 140 (Public Law 97 - 198), has designated February 11, the anniversary of the birth of Thomas Alva Edison, as National Inventor's Day
- In the Netherlands the major music awards are named after him.