Mark Fiore showed 'biting wit' in his cartoons, the Pulitzer board said
Online news organisations have for the first time won coveted Pulitzer Prizes, the top awards in US journalism.
A journalist writing in a collaboration between online news service ProPublica and the New York Times magazine won an award for investigative reporting.
Meanwhile, Mark Fiore of the San Francisco Chronicle's website won the award for editorial cartooning.
Pulitzer Prizes are awarded annually by Colombia University to honour the best in US literature, journalism and music.
Sheri Fink of ProPublica, a non-profit investigative journalism service, picked up one of two investigative journalism awards for her report about the urgent life-and-death decisions made by doctors at a New Orleans hospital in the days after Hurricane Katrina.
The article was co-published by The New York Times magazine - and was the first such collaboration to be recognised by the Pulitzer Prize.
"We are starting to see more and more of these partnerships," Sig Gissler, administrator of the Pulitzer Prizes, told the BBC.
"I expect we are going to see more of it in the years ahead, as organisations face tougher financial situations."
The award for Mark Fiore marked the first time internet-only based work has been recognised by the Pulitzer Prize committee.
His animated cartoons showed "biting wit, extensive research and ability to distill complex issues", setting "a high standard for an emerging form of commentary", the Pulitzer Prize board said.
The Washington Post picked up the most awards, winning the categories of international reporting, feature writing, commentary and criticism.
Country music singer Hank Williams was given a posthumous special citation recognising his lifetime achievement as a musician.
The National Enquirer - America's most notorious tabloid - failed to win an award, despite being nominated for its coverage of presidential candidate John Edwards' extra-marital affair.