On Oct. 4, 1986, Mexican singer/songwriter Juan Gabriel ranked at No. 1 on Billboard's newly created Latin Songs chart with "Yo No Se Que Me Paso."

Gabriel was already a superstar throughout Latin America, known for his eloquent, sugary balladry, and "Yo No Se Que Paso," with its synth keyboard and plethora of strings, epitomized the sound of the day: romantic, heartbroken, decidedly adult-skewing and largely imported from Mexico.

It was a time when Latin music and Latin culture overall in the United States were still oddities, flanked on the East Coast by the predominantly Cuban Miami and on the West Coast by predominantly Mexican California and Texas. Although there were occasional flare-ups of Latin beats, Latin music was niche, heard only on the Spanish-language radio stations that catered to predominantly Hispanic communities and found in the world music bins of stores like Tower Records.

TOP 25 LATIN ARTISTS 1986-2011

Fast forward 25 years: It's a dramatically altered landscape. The number of Hispanics living in the United States has more than doubled, from 22.4 million in 1990 to more than 50 million in 2010, according to the U.S. Census, and they are younger than the mainstream: 23.1% of children 17 and younger are Latinos. Hispanics, who constituted 9% of the population in 1990, now comprise 16.3%, officially the largest minority in the nation.

Pitbull's "Rain Over Me" (featuring Marc Anthony), the current No. 1 and the 325th in Latin Songs history.

And the music on Billboard's Latin Songs chart is now an amalgamation of styles, nationalities and even languages, led last week by reggaetón duo Wisin y Yandel's "Tu Olor." It's their eighth No. 1 on the chart, continuing a distinct sonic tendency; in the past year, the chart's longest-running No. 1 has been "Danza Kuduro" (15 weeks), which belongs to another urban artist, Don Omar.

TOP 25 LATIN SONGS 1986-2011

"Radio in general is becoming more variety-based as a result of [the Portable People Meter]," Univision Radio senior VP of programming J.D. Gonzalez says. "The same is happening in Spanish. Spanish listeners prefer a variety of tempos and a variety of textures. And that's what we're seeing on the chart. Listeners are less inclined to live in just one niche. They don't just live in regional Mexican or contemporary. The challenge is knowing how far we can push the boundaries."

Billboard debuted the Latin Songs chart (as the Hot Latin 50) in 1986 with a prominent story on the second page of the magazine, announcing a "new weekly Latin airplay chart" comprising the "top 70 Latin (Spanish-speaking) radio stations" in the United States and Puerto Rico. Stations were asked to report their playlists and adds weekly. The information was compiled via telephone and entered into Billboard's computer, with points assigned to positions and multiplied by the station's weight to determine the rank of each track. The Hot Latin 50 chart ran beneath Billboard's then-biweekly Latin Albums chart, which was segmented by genre: pop, tropical/salsa and regional Mexican. In comparison, the Latin Songs chart put all genres together under a single umbrella, and it quickly became the barometer of the Latin industry.

"Back then, if you weren't on the airplay chart, there was no sales development," says Lucas Pina, senior VP of SBS Entertainment, whose first industry job (in 1994) was as a radio promoter for PolyGram Records in the Northeast. "The Latin Songs chart told people what was new. Being on that chart was crucial. In the U.S., it was the difference between having credit or not."

NEXT: THE REGGAETON REVOLUTION