Events in History
Presidential Convention
May 1 Whig convention nominates Henry Clay as presidential candidate

Henry Clay
- May 6 Johan Thorbecke argues general right to vote
- May 23 Declaration of Bab (Baha'i festival) ('Azamat 7, 1)
Historic Communication
May 24 Samuel Morse taps out "What hath God wrought" in the world's first telegraph message

Samuel Morse
- May 25 1st telegraphed news dispatch is published in Baltimore Patriot
Birthdays in History
Elijah McCoy
May 2 Elijah McCoy, Canadian-American inventor of African descent, notable for his 57 US patents (lubrication of steam engines), born in Colchester, Ontario (d. 1929)

Elijah McCoy
- May 3 Édouard Drumont, French anti-semitic journalist, born in Paris (d. 1917)
- May 17 Julius Wellhausen, German biblical scholar (analysis of the structure and dating of the Pentateuch), born in Hamelin, Hanover, Germany (d. 1918)
- May 21 Henri Rousseau, French post-impressionist painter (The Dream, The Hungry Lion Throws Itself on the Antelope), born in Laval, France (d. 1910)
- May 22 Mary Cassatt, American impressionist painter (Woman Bathing), born in Allegheny City, Pennsylvania (d. 1926)
- May 23 `Abdu'l-Bahá, Successor to Prophet of the Bahá'í Faith (d. 1921)