At a rededication ceremony for the memorial, Associated Press Executive Editor and Senior Vice President Kathleen Carroll called on journalists to fight indifference and reaffirm the importance of standing up to corruption and fear.
If journalists fail to do so, she said, "then you are giving up things that these people died to fight for, and that's unconscionable."
"Across the world, journalists are not submitting. They fight for the right to freely chronicle the actions of the powerful and the humble," Carroll said.
The memorial now contains the names of 2,256 journalists who have died while covering the news since 1837, said Gene Policinski, Newseum chief operating officer.
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He said advances in digital media have put more journalists at risk, since they now have larger audiences and can attract more attention.
About 50 friends and relatives of journalists named on the memorial were present. Some reached for tissues as the circumstances behind the deaths were read.
Among the other journalists memorialised were: Akhmednabi Akhmednabiyev, 53, from Russia, killed for reporting on government corruption and human rights violations, Yasser Faisal al-Jumaili, 35, from Iraq, killed in Syria trying to film the civil war and Sai Reddy, 51, from India, who reported on a 20-year fight between Maoist rebels and police; he was killed when armed Maoist rebels attacked him.