BOB GARFIELD: From WNYC in New York, this is NPR's On the Media. Brooke Gladstone is away this week. I'm Bob Garfield. Last weekend, a half million people suddenly materialized out of thin airwaves. [CROWD CHANTING IN SPANISH]

MAN: Something is happening on the streets of this country, [SOUND OF DRUMS] something passionate and real and surprising.

BOB GARFIELD: How did so many converge to protest immigration legislation when the media had scarcely spoken of the rally beforehand? The answer is that the media were talking about the rally, the Spanish language media. They were all over this story for weeks, under the radar of the Anglo world but in the center of Latino lives. Just as much of the nation's Hispanic population lives in parallel to mainstream America, so too Hispanic media, which, like the weekend marchers, has revealed itself as a force to be reckoned with. Felix Gutierrez is a professor of journalism at the Annenberg School of Communications at the University of Southern California, and he's been studying Hispanic media for decades. He joins us now. Felix, welcome to OTM.

FELIX GUTIERREZ: Thank you for having me. It's good to be with you.

BOB GARFIELD: Well tell me briefly please, the history of Spanish language media as a rallying force on political questions.

FELIX GUTIERREZ: Well, it's a deep history here in Southern California. Last year we celebrated the 150th anniversary of El Clamor Publico, a newspaper literally named The Public Clamor, which was the first Spanish language newspaper here in Southern California. And in the 1850s, they were saying, “look the U.S. has come, they've taken our land, they've made us their citizens, they're lynching us, they're squatting on our land. We don't have equal rights.” Radio has had the same role in the 1930s. Pedro J. Gonzalez was a predominant radio personality here. This was the time of the repatriations, when Mexicans were being rounded up, put on trains going to Mexico during the Depression. And he spoke out on his radio station, actually was sent to San Quentin on trumped-up charges that were later withdrawn because the key witness against him admitted that she had been asked to lie by the district attorney. In the 1950s, with Operation Wetback, which was an Eisenhower administration roundup of Mexicans, you see La Opinion, the Spanish language newspaper here, taking a very different role in covering these issues than The Los Angeles Times. And in the 1970s, with the illegal alien scares, when Attorney General Saxby promised to round up a certain number of illegal aliens by a certain time, you see the Spanish media telling their people, “look here's what they're doing but here's what your rights are, so take care of yourself and be careful.”

BOB GARFIELD: Decades ago, the Spanish media had a role in mobilizing the community, but it's long since involved to become a very substantial industry. Tell me about the evolution and just how big Spanish media are, just for example, in Southern California.

FELIX GUTIERREZ: When I was doing my doctoral dissertation [LAUGHS] in the early 1970s, I decided to do it on Spanish language radio. And there were two radio stations here at the time in Spanish. And I remember when I went back to campus, one of the faculty members just said, “Why are you studying that? That's a dying medium.” Today there are 16, at least, radio stations in Spanish in the Los Angeles area, so the media have not died. They've grown. They've grown with the population, but most importantly, they grew because advertisers had an interest in reaching this audience. They went beyond the ethnic markets, the mom and pops. And the big advertisers now are, you know, McDonald's and the breweries and the same advertisers you see pretty much in English. Spanish language radio used to be a format. It was a medium of chance, not a medium of choice. You listened to the radio station because you preferred Spanish or you only spoke Spanish, and you only had one or two choices. Now it's a medium that's replicated English-language media in that there's a sports talk station, there's oldies stations, reggaeton, banda, rancheros, which is music from the northern part of Mexico, tropicales. So whatever flavor you want [LAUGHING] in Spanish, you can get it.

BOB GARFIELD: In Spanish-language media, is there a Rush Limbaugh, a Howard Stern, a 900-pound gorilla?

FELIX GUTIERREZ: What you see here is the emergence, a re-emergence of radio personalities. If you listen to so-and-so's show, they play music, they have guests who will do interviews, they take calls, tell slightly off-color jokes. But they play a multiple role. They comment on political affairs and current events and such. And that format has become very dominant here, particularly in drive time. So Humberto Luna, El Cucuy, which is another personality, El Piolin, who's the one who's taking credit for mobilizing the other personalities – in this case, they said, “let's work together.” Soon, there was 11 stations that signed up to say, “We're going to promote this as a good civic participation for our people.” I think what's different is that this has been a mass mobilization on one day. But over the years, the Spanish language media and other ethnic media have always given you the news and music that you might like from your home country, but also telling you here's how things work in the United States. Now, when I was listening to the Spanish-language radio last week, they were urging people to participate but also saying, you know, “bring the family, show your best side, don't get drawn into a confrontation; there may be people there who will try to provoke us.” So it was encouraging people to be there but to show their best face and not to be, you know, the kind of people that we've really been baited to be by some of the English-language media. What I'm seeing now is that this is becoming a more balanced debate. Rather than being the targets or scapegoats of the right-wing talk shows and conservatives, which undocumented people have been for years, they're speaking out in their own voice, and people are seeing another side of this community that they haven't seen in much of the media over the years.

BOB GARFIELD: Felix, thank you very much.

FELIX GUTIERREZ: Okay. Well, thank you.

BOB GARFIELD: Felix Gutierrez is a professor of journalism at the Annenberg School for Communication at the University of Southern California.