11. Corner of West Houston Street and Varick Street, New York City, 1890.
12. A photograph of the now-damaged portion of Notre Dame taken between 1851 and 1870.
13. Opera Singer Mary Garden, 1908.
14. In honor of 4/20: the iconic Hollywood sign altered by Cal State Northridge student Danny Finegood as part of an art project (he got an A), 1 January 1976.
15. 20 years ago, the infamous Columbine High School massacre occurred on 20 April 1999.
Here, four young women headed to a library near Columbine High School where students and staff members were evacuated, after two gunmen opened fire inside a school in the suburb of Littleton, Colorado.
16. The British Concorde fleet in one picture, 1986.
17. A soldier gives two Germans he captured at the Battle of El Alamein the traditional British salute, 26 October 1942.
18. Negotiation between the zoo director and escaped chimpanzee, Belgrade, 1988.
19. Two German soldiers and their mule wearing gas masks, 1916.
20. Indigenous Ainu man of Japan.