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This Day in American History

October 21

1 historic event on this date

Historical1879

Edison Tests the Incandescent Light Bulb

Thomas Edison successfully tested a practical incandescent light bulb at his Menlo Park laboratory, achieving over 13 hours of continuous light. His invention, protected by U.S. Patent No. 223,898, would transform American life and industry.

Why It Matters

Edison's invention demonstrated the power of America's patent system to incentivize innovation, a principle embedded in the Constitution's intellectual property clause.

Explore the Principles Behind the History

Every event in American history connects to the founding principles. Discover the ideas that shaped these moments.

View the 28 Founding Principles