Tijuana's Jai Alai Fronton Palace: Photograph by Christopher Reynolds / Los Angeles Times

Tijuana's Jai Alai Fronton Palace (Photograph by Christopher Reynolds / Los Angeles Times)

It's dusk in Tijuana's red-light district, and two bouncers are slouching outside a strip joint called the Chicago Club. A car rolls up, a window rolls down, and the American guy on the passenger side starts asking questions in awkward Spanish. Looks like business as usual.

But then I climb out of the passenger seat—that's right, it's me in the car—to make sure they hear me right.

"That sign across the street," I say, pointing toward the towering words MOLINO ROJO in scarlet neon. "From what year is it?"

The guys look at each other. They have seen many things on this block, but an architectural preservation tourist, it seems, is not one of them.

"From the '30s?" I ask hopefully.

They squint across the street and scoff.

"Fifties or '60s," one of them finally says.

Bummer. And welcome to the search for the Tijuana of the '20s and '30s—the city that was Vegas before Vegas was Vegas, the city that some Tijuanenses pine for and others treat like incriminating evidence. This bygone Tijuana lives on in tattered postcards and historical-society monographs, its casinos paying off in American silver dollars, its horse-track bettors forever tempted by the prospect of a nightcap at the world's longest bar.

Looking for remnants of that place in 2007 is like diving for a Mexican Atlantis. Instead of checking out the hotels and fancy restaurants along the fast-growing Baja coast, you squint at history through a veil of border culture and discarded architecture, the whole scene scented with carnitas and beer.

The casinos are the key. If you persevere, you can learn why a Muslim mirage rises over the heart of Tijuana today and how two enduring trophies of 20th century high life, the Caesar salad and the margarita, were born or adopted here.

And you can wonder: What if Baja's old casinos had endured? Would Vegas be Phoenix? Would the strip run from Tijuana to Cabo San Lucas? Would Mexico be corrupted? (Oh, wait.)

By now the world takes for granted Tijuana's reputation as a den of forbidden thrills (or, as Krusty the Clown on "The Simpsons" puts it, "the happiest place on Earth"). Yet until I came across a new book by Los Angeles writer and preservationist Chris Nichols titled "The Leisure Architecture of Wayne McAllister," I'd never thought much about the roots of that reputation or the Tijuana-Vegas connection. In the course of telling how McAllister landed the job of designing a long-lost resort called Agua Caliente—at the advanced age of 19—Nichols sketched a bigger picture that explained a lot.

From 1919 to 1933, alcohol and casinos and prostitution and horse racing were all forbidden or tightly restricted in California, and all were easily available in Tijuana. Because of that, great pleasure palaces were built, including the city's fabled Agua Caliente casino, and countless Hollywood celebrities and their imitators crept south by car, rail, ship and small plane.

One Times reporter, surveying the Agua Caliente casino in 1929, concluded that "there isn't another place on the continent, outside of a U.S. mint, where you can see so much money piled up before your eyes at one time. Its only rival in the world is Monte Carlo."

That casino was the crown jewel of the era. It opened in 1928, tiled and stuccoed, Moorish and missionary, vast and self-assured. It lay six miles south of the border, covered 655 acres and cost about $10 million at the time, the lion's share supplied by American investors. It was "one of the most opulent resorts ever to grace the Americas," writes Nichols, "but more significantly, it was the inspiration for Las Vegas."

Along with a casino offering roulette, baccarat and faro (but no windows or clocks), it featured about 400 rooms and bungalows, a horse-racing track, a golf course, a spa fed by natural spring water (hence the name), an Art Deco ballroom, various cocktail bars, tennis courts, a riding academy, a landing strip for small planes, a blue-tiled minaret and an iconic bell tower, a replica of which now stands at the beginning of Boulevard Agua Caliente.

Charlie Chaplin and Gary Cooper came to the races. Douglas Fairbanks sat on the board of directors. Jean Harlow tried the golf course. Bing Crosby and Clark Gable saddled up horses, and the showroom featured a teenage dancer, Margarita Cansino, who later changed her name to Rita Hayworth.

Architectural Digest gave it 16 pages in 1929. Hollywood gave it a movie—"In Caliente," featuring Dolores del Rio and Pat O'Brien, shot on location in 1934.

But by then the cards had started falling another way. Nevada legalized gambling in 1931. The U.S. ended Prohibition in 1933. Santa Anita racetrack opened in Los Angeles County in 1934. In 1935, newly elected Mexican President Lázaro Cárdenas banned casino gambling. (One of the leading casinos of that era, historians say, was a downtown venue called the Molino Rojo. A school replaced it, but as the sign I saw attests, another entrepreneur has revived the name at a new location.)