Ethel and Julius Rosenberg were the first American civilians to be executed for espionage. They were charged with transmitting secret information about the atomic bomb to the Soviet Union, and convicted of conspiracy to commit espionage during a time of war.
On April 5, 1951, the Rosenbergs were sentenced to death. The couple was executed by electric chair just before sunset on June 19, 1953.
St. Louis Post-Dispatch
New York Times