After the war he established the Naval Research Laboratory, the only American institution for organized weapons research until World War II.

With Henry Ford and the Firestone Company, Edison organized the Edison Botanic Research Company in 1927 to discover or develop a domestic source of rubber. Some 17,000 different botanical specimens were examined over 4 years—an indication of Edison's tenaciousness. By crossbreeding goldenrod, he developed a strain yielding 12 percent latex, and in 1930 he received his last patent, for this process.

To raise money, Edison dramatized himself by careless dress, clowning for reporters, and playing the role of homespun sage with aphorisms like "Genius is 1 percent inspiration and 99 percent perspiration" and "Discovery is not invention." He scoffed at formal education, slept only four hours a night, and often worked 40 or 50 hours straight. As a world symbol of Yankee ingenuity, he looked and acted the part. Edison had more than 10,000 books at home and masses of printed materials at the laboratory. When launching a new project, he wished to avoid others' mistakes and to know everything about a subject. Some 25,000 notebooks contained his research records, ideas, hunches, and mistakes. Supposedly, his great shortcoming was lack of interest in anything not utilitarian; yet he loved to read Shakespeare and Thomas Paine.

Edison died in West Orange, New Jersey, on October 18, 1931. The laboratory buildings and equipment associated with his career are preserved in Greenfield Village, Detroit, Michigan, thanks to Henry Ford's interest and friendship. .