32 Scientific American, March 2021
STEVE SCHAPIROGetty Images( top);^HULTON ARCHIVEGetty Images( bottom)POSTER at a Selma-to-
Montgomery march in 1965
protested the killings of
Black people by police.MORE THAN 200,000
people participated in the
March on Washington on
August 28, 1963, where King
articulated the aspirations of
millions with his famous
“I Have a Dream” speech.