- May 2 Argentinian Domingo Sarmiento publishes his anti-tyranny work "Facundo Civilización y Barbarie"
- May 3 1st African American lawyer, Macon B. Allen, admitted to the bar in Massachusetts
- May 3 Fire kills 1,600 in a popular theater in Canton, China
- May 14 Utrecht-Arnhem Railway opens
- May 20 1st legislative assembly convenes in Hawaii
- May 20 HMS Erebus and HMS Terror with 134 men under John Franklin sail from the River Thames in England, beginning a disastrous expedition to find the Northwest Passage. All hands are lost.
- May 23 New York City Police Department (NYPD) is formed, replacing an old night watch system
- May 28 Fire in Quebec, Canada, 1,500 houses destroyed
Authors
Dictators
Explorers
Outlaws
Queens
Spies