A clown performs next to the Monument to the Revolution as he takes part in the Latin American Clown Convention in Mexico City, Mexico, October 21, 2015. The convention will be held from October 19 to 22 in Mexico City. (Photo by Henry Romero/Reuters)

Ricky Martin perfoms "La Mordidita" during the Latin Recording Academy Person of the Year gala honoring Brazilian singer Roberto Carlos in Las Vegas, Nevada November 18, 2015. (Photo by Mario Anzuoni/Reuters)

An armoured vehicle surrounded by Chicago cops at the time of the American depression, 1933. (Photo by Rolls Press/Popperfoto/Getty Images)

Recording artist Yeini arrives at the 17th Annual Latin Grammy Awards in Las Vegas, Nevada, U.S., November 17, 2016. (Photo by Steve Marcus/Reuters)

A British Museum representative poses for photographs next to Andy Warhol's “Mao”, left, and Jim Dine's “Drag: Johnson and Mao” which feature in “The American Dream: pop to the present” exhibition during a media photocall at the British Museum in London, Monday, March 6, 2017. The exhibition, which opens to the public from March 9 and runs until June 18, charts modern and contemporary print making. (Photo by Matt Dunham/AP Photo)

Frank A. Rinehart, a commercial photographer in Omaha, Nebraska, was commissioned to photograph the 1898 Indian Congress, part of the Trans-Mississippi International Exposition. More than five hundred Native Americans from thirty-five tribes attended the conference, providing the gifted photographer and artist an opportunity to create a stunning visual document of Native American life and culture at the dawn of the 20th century. Photo: Little Bird, Arapahoe, 1899. (Photo by Frank A. Rinehart)

Gus Palmer (Kiowa, at left), side gunner, and Horace Poolaw (Kiowa), aerial photographer, in front of a B-17 Flying Fortress. MacDill Field, Tampa, Florida, ca. 1944. (Photo and caption by 2014 Estate of Horace Poolaw)

Tank crew standing in front of M-4 tank, Ft. Knox, Kentucky, June, 1942. (Alfred Palmer/OWI/LOC)