![A St. Louis police officer stands atop a SWAT vehicle.](/sites/default/files/styles/large/public/Sharpshooter_facing_camera.jpg?itok=NzPFnXHv)
Police Sharpshooter, Ferguson Protests
![NYPD, 1964.](/sites/default/files/styles/large/public/Screen%20Shot%202015-03-12%20at%201.20.21%20PM.png?itok=OtOru6f6)
NYPD, 1964
Photo provided by author, from Library of Congress.
![A group of demonstrators stand at a Ferguson, Missouri protest holding signs that read 'Hands Up, Don't Shoot.'](/sites/default/files/styles/large/public/Protesters_with_signs_in_Ferguson.jpg?itok=IrxALFYy)
Ferguson, Missouri Protestors
![Artist William Johnson depicts of the Harlem Riot, 1943 in this piece called Moon Over Harlem.](/sites/default/files/styles/large/public/Moon_Over_Harlem.jpg?itok=rS-MCWGh)
Harlem Riots, 1943
Million Hoodie March, 2012
![Nancy Reagan hosts the First Lady's conference on drug abuse at the White House, 1985.](/sites/default/files/styles/large/public/NREASTROOM.jpg?itok=S8JU1rif)
Nancy Reagan, "Just Say No Campaign"
![An August 2014 'Light Brigade' stands with Michael Brown near Red Arrow Park, Milwaukee.](/sites/default/files/styles/large/public/14736904320_94cb2c10d2_z_0.jpg?itok=b_0F-tJg)
"Light Brigade" Protest, 2014
![During the Harlem Riots of 1964, demonstrators carry leaflets of Lieutenant Thomas Gilligan who shot and killed 15-year-old James Powell, a black student.](/sites/default/files/styles/large/public/800px-Demonstrators-Harlem-1964_0.jpg?itok=RCW9HOCf)
Harlem Riots, 1964
![Police confront a demonstrator during the Harlem Riots of 1964.](/sites/default/files/styles/large/public/509px-Harlem_riots_-_1964_0.jpg?itok=CVXY5ZgX)
Harlem Riots, 1964
![President Lyndon B. Johnson meets with Civil Rights Leaders Martin Luther King Jr., Whitney Young, and James Farmer.](/sites/default/files/styles/large/public/800px-Lyndon_Johnson_meeting_with_civil_rights_leaders_0.jpg?itok=oGHvqw4z)
Lyndon B. Johnson & Civil Rights Leaders
![A soldier stands observing the aftermath of a race riot in Washington D.C., 1968.](/sites/default/files/styles/large/public/1024px-Leffler_-1968_WashingtonDC_MLK_riots_0.jpg?itok=GtLOQKgj)
Washington D.C. Race Riots, 1968
![President Lyndon B. Johnson meets with Richard Nixon.](/sites/default/files/styles/large/public/800px-Lyndon_Johnson_Richard_Nixon_1968_0.jpg?itok=qew18A8N)
President Lyndon B. Johnson & Richard Nixon
![Protestors at a Black Lives Matter demonstration in New York City, November 2014.](/sites/default/files/styles/large/public/Black_Lives_Matter_protest.jpg?itok=eUAf4nb7)
Black Lives Matter, New York City
![Protestors in Chicago, Illinois rally against Staten Island grand jury's decision in Eric Garner case.](/sites/default/files/styles/large/public/Eric_Garner_Protest_Chicago_Dec_4_2014.jpg?itok=YH4sdiYQ)
Black Lives Matter Protest, Chicago