Veteran U.S. television anchor Ted Koppel stepped down from ABC News last week. His retirement--following the departure of all three major U.S. broadcast television news anchors within the past year--marks the end of an era. Leta Hong Fincher has more on the challenges network news faces, and how television news might look in the future.

Tom Brokaw, NBC News

NBC News anchor Tom Brokaw was the first to go.

"Thanks for all that I have learned from you, that's been my richest reward," he said on his final broadcast.

Then CBS News anchor Dan Rather stepped down.

"I believe my best work is ahead of me," Mr. Rather said.

Peter Jennings, ABC News

ABC News anchor Peter Jennings had a tragic and sudden death.

"I have learned in the last couple of days that I have lung cancer," said Mr. Jennings earlier this year.

'Nightline' anchor Ted Koppel prepares for the taping of his last broadcast, Tuesday, Nov. 22, 2005

And now, the venerated ABC News anchor Ted Koppel has left too.

"I'm Ted Koppel and this is Nightline."

All four newscast hosts, or anchors, played pivotal roles in U.S. broadcast news since the 1960s, transforming the news from a second-hand, print-based medium to something that allowed the American public to witness landmark events for themselves.

Dan Rather, CBS News

"We just have a report from our correspondent Dan Rather in Dallas that he has confirmed that President Kennedy is dead," announced anchor Walter Cronkite in 1963.

Mr. Cronkite had by the late 1960s become known as the most trusted man in the United States. He and successive anchors were national icons, showing the public what was important in the world.

Today, millions of Americans still watch the morning and evening network newscasts, but their audience is nowhere near as large as it used to be. Part of that is due to the growth of 24-hour cable news networks, which offer constant news updates, meaning people don't have to wait for a network newscast.  

Another reason is changing demographics: over the last two decades, the average age of the network news viewer has climbed, as younger viewers turn to other sources of information.

Deborah Potter, NewsLab

Deborah Potter is director of NewsLab, a broadcast news research center in Washington D.C.  She told us, "The big challenge I think for the networks is to figure out a way to draw those viewers in before quite frankly their viewership dies off, because the way the trend is going, all of those viewers will be gone one day and if they can't replace them with younger ones, they're going to be in really serious trouble."

Ms. Potter says that to fight declining audience numbers, the networks are exploring new ways of communicating with people--and that includes doing away with the traditional role of anchor as the "voice of God".

ABC News Nightline, for example, is replacing anchor Ted Koppel with three hosts. CBS News and ABC News have still not announced what changes will be made to their evening newscasts.

Traditional television content is now available on the Web

To attract younger customers, all the networks have developed rich online sites. They have set up "Web logs" or "blogs" that promote interaction among viewers. They have also begun "podcasting," allowing newscasts to be downloaded onto a portable device such as an iPod and watched on demand.

Ms. Potter says the networks are increasingly seeking input from their viewers as well.

"I think the networks have realized, although they're late to the party, that their viewers know an awful lot and could in fact be sources of news---contributors to news, not just consumers of news."

After July's terrorist bombings in London, for instance, networks solicited video and pictures from people who had captured the blasts on their mobile camera phones. News divisions incorporated this amateur footage into their formal reports.

Andrew Nachison, Media Center

Andrew Nachison, head of the Media Center research group in Reston, Virginia, says greater participation from citizens is changing the traditional relationship between television news producer and consumer.

"The old model was, ‘here's the story, take it or leave it,’ and the new model is, ‘here's what we think the story is, please tell us if you know more, and let us know if we've gotten anything wrong’."

Video news is now available on portable computer devices and mobile phones

Mr. Nachison argues that the network evening newscast may be dying, but news transmitted through television is becoming more popular than ever.

"Let's call it video news, let's call it broadcast news or whatever you want to call it. It's going to come over satellites, cable, phones, your computer, it's going to come over all sorts of devices, but if we call that television news, I think organizations that produce news through video will have lots of work," he said.

Most media analysts agree that whatever the fate of the networks, the era of television--in all its forms--is just beginning.