When the United States entered World War One , Edison and his staff at West Orange responded with fierce patriotism. Edison submitted more than forty plans and inventions to the navy for their consideration during the war. Many of his suggestions were very useful, although the navy was careful not to let him know that. One of his major contributions was the simple suggestion that submarine sinkings be plotted on a map in order to discover where high-risk areas lay.

Edison was selected to head the Naval Consulting Board, a link between the navy and the scientific civilian community, in 1915. But while Edison was enthusiastic about the chance to support his country through inventions, he disliked the stiff environment of the navy especially when his ideas and suggestions were pigeonholed or rejected by naval officers. He resigned from the board over a fiasco involving a research laboratory. Edison originally suggested the idea, believing a facility devoted to military research and development would be invaluable to the war effort, but Edison ended up clashing with the navy and the rest of the board over the location and administration of the laboratory. In the end, the navy agreed to build a laboratory but did not do so as Edison wished. He resigned from the board in a huff in December 1920.

These days, public work was less important to Edison than spending time with his family. For the first time ever he began to go home for dinner, and he found in his wife, Mina Miller, a wonderful companion. He primed his son, Charles Edison, to take over Thomas Edison, Inc. Charles Edison did take over the company upon his father's death, and he ran it efficiently until 1957, when it was sold to McGraw Electric Company.

He also found a new friend in Henry Ford, the automobile magnate. Ford had been an admirer of Edison for many years, before he invented the Model T and became a wealthy, well-known industrialist himself. In 1907, a year before the Model T came out on the market, Ford had even sent Edison a request for a photograph. He claimed he wanted to have photographs of "three of the greatest inventors of this age" in his den at the factory. The two men met in 1896 and were good friends throughout the 1910s and 1920s. They even took a series of gypsy car trips over the United States, providing the press with delightful photo opportunities. They had much in common in regards to business practices and the industry of invention. Sadly, they also shared the same anti-Semitism.

When Thomas Edison died on October eighteen, 1931, he left behind an incredible legacy. That legacy cannot be measured simply in the 1,093 patents he had accumulated, or the millions of dollars he earned (and spent!) in his lifetime. It is easier to measure by walking into a room, flipping a switch, and noting what has happened since Edison first hit upon his light bulb idea.

Edison's involvement with the U.S. Navy was a brief reminder of what he had detested as a child and as a young man: rigid structure and authority. The Navy's stiff policies and bureaucracy hemmed Edison in, and he revolted against it from the beginning. At first, his feelings of patriotism kept him devoted to the project, but when it became clear that his ideas and suggestions would not receive the same value as they did in his own business, he left.

Charles Edison was a worthy successor to his father in many ways. Though he did not have the same tirelessly creative mind, he possessed a strong work ethic and good business sense. These qualities kept Thomas Edison, Inc. afloat during the hard days of the Great Depression and the enormous changes in technology after World War Two . Later in his life, Charles Edison had a brief career in government. Ironically, he was elected Secretary of the Navy in 1940.

Edison's death also marked the end of an era in American business. No longer was there the freedom for a lone inventor to build an empire as Edison had done. Structural changes in the economy, as well as the upheavals of the new century, had altered the fabric of American business enterprise forever.