Panama Canal Authority
- The United States pursues canal rights over the isthmus of Panama from Columbia, but is rebuffed. With U.S. backing, Panama becomes independent, and signs a treaty to allow construction of the Panama Canal.
- Theodore Roosevelt holds office as the 26th president of the United States.
- Congress creates the U.S. Department of Commerce.
- The U.S. Navy establishes a base at Guantanamo, Cuba.
- Al Smith wins a seat in the New York State Assembly.
- The village of Lake George is incorporated.
- Congress establishes the first national wildlife refuge on March 14, 1903 at Pelican Island, Fla., to protect declining populations of pelicans and other water birds.
- Alexander Obrenovich, king of Serbia, and his wife, Draga, are murdered in a military coup.
- The New York State Legislature passes the Compulsory Education Act of 1903, a model for laws limiting child labor.