Wikipedia:Selected anniversaries/May 20
On May 20:
- 325 - The First Council of Nicaea was formally opened.
- 1498 - Portuguese explorer Vasco da Gama arrived at Calicut, India.
- 1570 - Abraham Ortelius issued the first modern atlas.
- 1862 - U.S. President Abraham Lincoln signed the Homestead Act into law.
- 1882 - The Triple Alliance was created between Germany, Austria-Hungary and Italy.