Before  the  1980s, the three national  broadcast net­works-ABC, CBS, and  NBC-were  the  gatekeepers of  news on  television  in  the  United  States. At 6:30 P.M. Eastern Time, Monday through Friday, each of the three majors presented 22 minutes of news (plus commercials) to the nation from their headquarters in New York. When, in 1980, Atlanta-based cable entrepreneur Ted Turner launched CNN (Cable News Network), a round-the-clock, all-news network reaching 1.7 million cable television households, skeptics said he would never come up with enough news to fill 24 hours of programming. CNN was widely maligned as "Chicken Noodle News." But over the next two decades, CNN came to redefine what qualifies as news, what news viewers demanded, and  what sort of  news  programming both cable and broadcast networks provided, in the United States and around the world.

     Although CNN failed to turn a profit in its first five years, it continued to expand and diversify, with the launch of CNN Headline News in 1981 and CNN International on 1985. A few news events proved to be major milestones for CNN, and for the public's understanding and growing viewership of "news on demand." In 1986, when the space shuttle Challenger exploded shortly after takeoff, CNN was the only network airing live coverage of the launch-and, therefore, of the crisis. By 1989, CNN reached 50 million U.S. television households. But the network truly came of age in 1991, when it was the only network to report live from the Iraqi capital on the opening night of the Persian Gulf War, and a worldwide audience of one billion people-some of the largest in television history for a non-sporting event-tuned in.  Later  that year, Time magazine recognized Turner, CNN's founder, as its "Man of the Year." By 1996 , CNN had been acquired by media giant Time Warner, and it was more profitable than the three major networks' news divisions combined (though its ratings have, over the years, remained at a fraction of the overall ratings of ABC, CBS, NBC, and Australian media tycoon Rupert Murdoch's relative newcomer FOX network).

     CNN has garnered praise for its focus on international news, maintaining many more overseas bureaus than its U.S. competitors. It has also been cited as emblematic of an era in which information has proliferated but knowledge is ever  more  scarce-and television news standards have degenerated. In the 1990s, the network drew many viewers, but also much criticism, for its in-depth coverage of events that never would have gained such attention from the broadcast networks-its live cablecast of the 1992 press conference in which Gennifer Flowers revealed her affair with presidential candidate Bill Clinton, for instance, or its gavel-to-gavel coverage of the criminal trial of celebrity sports figure O.J. Simpson. CNN's ratings soared during such high-profile events, but diminished considerably once the events had played out.

     Still, by the mid- 1990s, major media outlets were scrambling to reinvent themselves in light of CNN's ascendancy. The U.S. broadcast networks could not compete with CNN in terms of immediacy or range of coverage, so their national news broadcasts began to focus on fewer stories with more analysis, as well as on "soft" news relating to health and lifestyle trends.

     In 1995-96, ABC, NBC, and FOX each announced plans to launch their own 24-hour news networks. ABC's project died on the drawing board. But FOX News Channel and MSNBC, a collaboration between NBC and high-tech corporation Microsoft, remain CNN competitors to this day. Both of these newer networks defined themselves in contrast to CNN's style and content. While CNN' s viewers tend to be close to or older than the legal retirement age, MSNBC went for the coveted 25-to-54 demographic with slick sets and a more youthful focus. From the outset, MSNBC emphasized the synergy between its television channel and website, with an eye toward the future of 24-hour news on the Internet. FOX's Murdoch has long complained about the "liberal bias" of the news media (and of CNN in particular), and his FOX News Channel, while promising "fair and balanced" coverage, tends to reflect its owner's conservative politics, most notably in the popular opinion program The O'Reilly Factor, with vitriolic host Bill O'Reilly. By early 2002, FOX News boasted a daily viewership of 654,000; CNN, 595,000; and MSNBC, 295,000. FOX's edge was particularly significant because that channel was available in 9 million fewer homes than CNN's total of 86.2 million.

     Following a different trajectory from the other cable news networks, non-profit C-SPAN was founded in 1979 as a public service by a group of cable industry executives. It began 24-hour-a-day programming in 1982, and C-SPAN 2, launched in 1986, went to 24 hours in 1987. The channels' position in the cable landscape began to look uncertain after the 1992 cable act's "must-carry" provision led some cable operators to drop C-SPAN to make room for broadcast stations they were now required to carry, and again in 1996, when Rupert Murdoch offered the country's largest cable company, TCI (TeleCommunications, Inc.), the unheard-of price of $11 per subscriber to carry his FOX News Channel. But after an impassioned letter­ writing campaign among C-SPAN fans, an op-ed onslaught by C-SPAN head Brian Lamb, and a change of leadership at TCI, C-SPAN ended the 1990s in a more secure position. In 2002, C-SPAN reached 86.5 million subscribers.

     Local all-news cable channels-some owned by cable companies, others owned or operated by major daily newspapers, and still others independent ventures-began to enter the fray as early as  the  late 1980s, and continue to grow in number. At the other end of the spectrum are international 24-hour news channels like BBC World and EuroNews, launched by a consortium of European public service broadcasters, competing in the global market with CNN International and maintaining a non-U.S.-centric perspective on world news. In mid-2003, BBC World (launched in 1995) was available in more than 250 million homes in over 200 countries; its success is attributed to a combination of its ability to use the full resources of BBC News-the largest broadcast news-gathering organization in the world-and the careful localization of its non-news programming to reflect the varying interests of its regional markets .

     Many commentators point to the fact that the advent of 24-hour news has shaped more than how viewers understand their world. The tenn "CNN effect" is used in two ways. One sense refers to a drop in consumer spending when people stay home to watch the news during a crisis. The sense in which the "CNN effect" (or "CNN factor" or "CNN curve") is more commonly employed, however, refers to the diplomatic repercussions of widely available news on demand. To what degree does instant news or continuous coverage of an event affect foreign-policy decisions? Are officials more likely to intervene in far-off conflicts-and possibly make over-hasty choices-if the events are immediately visible on TV? In this view, 24-hour news marks an important chapter not only in media history, but in world history.