Rosario called Chávez's unbeaten record a lie. Chávez stopped him in the 11th

On the eve of the fight, UPI's report began with the champion's verdict. "Julio Cesar Chavez's 54-0 record is one big lie to World Boxing Association lightweight champion Edwin Rosario." "All his fights have been against non-name opponents," Rosario said. "Chavez made a record against guys right out of the bar." He also said: "They took him by the hand and built his record."

"He better knock me out," Chávez replied, "because if he doesn't, his bed will be too small for him to crawl under."

The railway carriage

Julio César Chávez was born on 12 July 1962 in Ciudad Obregón, in Sonora. His father, Rodolfo, worked for the railway, and when he was a small child the railway moved the family to Culiacán, in Sinaloa. It was a large family, and Chávez and his elder brother Rodolfo both say they lived in a railway carriage. "Vivíamos en un vagón de tren," Chávez said: we lived in a railway carriage. In his brother's memoir the family arrives at a railway wagon with four bunks and a small kitchen.

"We weren't starving," Chávez said, "but there was a lot of need." His mother, Isabel, wanted her sons to study, not box, and she took in other people's washing and ironing. "I saw my mom working, ironing, and washing people's clothes," he said, "and I promised her I would give her a house someday."

Two of the older boys, Rafael and Rodolfo, were boxers, and Rodolfo turned professional in 1971. "I really started because I had a couple of older brothers, Rafael and Rodolfo, who boxed," Chávez said. Juan Antonio López, a former WBC-ranked super-bantamweight, later said he had discovered him and that Chávez had first preferred football or baseball. According to Sports Illustrated, Chávez studied civil engineering at the State University of Sinaloa, but he was poor, and he quit to box.

He started as an amateur at 16 and had about 14 amateur fights. After losing a decision to Diego Ávila that he thought was biased, he turned professional.

The asterisk

Chávez had his first professional fight in Culiacán on 5 February 1980, aged 17, and knocked out Andrés Félix. "I fought a very experienced boxer, I didn't feel like fighting again," he said years later. "Luckily they stopped the fight and that motivated me."

His manager was Ramón "Zurdo" Félix. The early fights were in Culiacán and Tijuana, against lesser opponents.

His 12th fight, in Culiacán on 4 March 1981, is the one with the asterisk. He was 11–0. At the end of the first round he knocked Miguel Ruiz down with a punch the referee ruled had come after the bell, and Chávez was disqualified. The next day the Culiacán boxing commission overturned the result and made it a first-round knockout win. Ramón Félix, his manager, sat on that commission. "It was officially overturned the next day by the Culiacan Commission and changed to a KO-1 for Chavez," ABC's Bob Yalen told the Los Angeles Times in 1990. The record shows a win.

Champion at 22

By 1984 he had been unbeaten in more than 40 fights. On 13 September he fought Mario Martínez at the Olympic Auditorium in Los Angeles for the WBC super-featherweight title, which Héctor "Macho" Camacho had vacated on moving up to lightweight. The WBC rated Martínez No 1 and Chávez No 2. Martínez was the favourite. That year he had knocked out the former WBC champion Rolando Navarrete and Roberto Castañón, and, in the words of the WBC president Mauricio Sulaimán, he was "experiencing a great moment in his career, with 20 fights without a loss".

Martínez was the busier man early. In the fourth and fifth rounds Chávez wobbled him with a right, by the sixth Martínez was bleeding, and by the end of the eighth he was tiring. Chávez stopped him and was a world champion at 22.

In the United States it drew little attention. According to The Fight City, the title win "had sparked little interest" in the American mainstream. Mexican boxing was looking for a successor. "The 70s and early 80s were vintage years for Mexican fight fans with Carlos Zarate, Ruben Olivares, Miguel Canto, Lupe Pintor, Pipino Cuevas and Salvador Sanchez all establishing themselves as dominant champions," The Fight City wrote. By 1985 that generation had gone. Chávez's trainer, Cristóbal Rosas, had worked with one of them. Over his career Rosas guided four Mexican world champions: Romeo Anaya, Salvador Sánchez, José Duarte and Chávez.

Don King and Roger Mayweather

By 1985 Chávez was with Don King. Mort Sharnik, who programmed boxing for CBS, talked to King, and King set up a fight with the former WBA champion Roger Mayweather. It was first planned for a bullring in Tijuana. "What I hear," Sharnik said, "King thought they were talking dollars when they were talking pesos."

It went to the Riviera in Las Vegas instead, on 7 July 1985. Chávez was 22 and Mayweather 24. Mayweather boxed well in the first round. In the second Chávez closed the distance and started countering the jab with his right hand. He put Mayweather down twice, and the referee, Richard Steele, stopped it at 2:30 of the round. "This young man is for real!" said the television commentator Tim Ryan.

Around the world

Chávez defended the title in Las Vegas, Paris, New York, Monaco, Nîmes and Tijuana. On 3 August 1986, at the Stade Louis II in Monaco, he fought the former champion Rocky Lockridge. Chávez got off to the better start, according to The Ring, "mixing in some savage uppercuts with body punching", and Lockridge "momentarily froze his unbeaten foe with a right in Round 8". Chávez won a majority decision, 119–113, 116–113 and 116–116.

In December he defended against Juan LaPorte, the former WBC featherweight champion from Puerto Rico, at Madison Square Garden on the card of Tim Witherspoon against James "Bonecrusher" Smith. LaPorte was cut under the left eye in the second round, his nose was bloodied in the sixth and he was cut over the right eye in the 11th. Chávez lost a point for a low blow in the ninth, and from the fifth round to the 11th he did not lose a round on any of the three cards. He won 115–114, 114–113 and 117–112.

Before he defended against Danilo Cabrera in Tijuana in August 1987, Chávez announced that it would probably be his last fight at super-featherweight. That autumn, he said, he would challenge Edwin Rosario.

"They took him by the hand"

Rosario was 24, a Puerto Rican in his second reign as WBA lightweight champion. He had won the title 14 months earlier by knocking out Livingstone Bramble in the second round, and in 1986 he had lost a split decision to Camacho. He was a puncher, and he said Chávez had only taken the fight because King pushed him into it.

"I'm the first real fighter he's going to fight," Rosario said. On the day of the fight he added: "I'm not too good in English, but I'm a terror in Spanish and with my fists."

Chávez said he had fought 21 times at 135lb and won 20 of them by knockout. "I wouldn't have signed for the fight if I was afraid of him," he said. "He's going to get scared when he hits me with his best shot and nothing happens."

Las Vegas, 21 November 1987

The fight was in the outdoor stadium at the Las Vegas Hilton, over 12 rounds, on HBO. Rosario was paid $500,000 and Chávez $200,000. Chávez weighed 134¾lb and Rosario 135lb. The crowd was 8,580, and Chávez went in as the favourite.

He worked inside and hit Rosario with combinations to the body and the head all night. He landed 61 per cent of the 743 punches he threw, and Rosario 36 per cent of 731. Rosario was badly hurt in the eighth. By the tenth, Boxing News reported, his "left eye had been hammered shut, he was cut inside the mouth and spitting blood". Chávez was hardly marked. He led 98–92, 99–91 and 100–92 on the cards.

Late in the 11th Rosario's corner threw in the towel. Chávez was the WBA lightweight champion. Augustin de Valdez, the promoter who had paid him for his first professional fight, said later that he heard Rosario tell his corner: "I can't feel my arms anymore."

"The notion that Julio Cesar Chavez's 54-0 record was the product of fighting bums in Mexico was dismissed in a chilly desert arena Saturday night," UPI's report began.

"He started to talk too much, that he was going to knock me out and send me back to Mexico," Chávez said. "I knew in my heart he was scared and that I was going to beat him." He added: "I can't say it was my hardest fight, but it was a tough, hard fight."

"Chavez is a truly great fighter," said Jim Jacobs, Rosario's co-manager. "It's no disgrace to lose to a fighter this good."

In February 1988 Sports Illustrated wrote: "He has the traditional Mexican strength-sapping short punches to the body and also the knowledge of how to use his shoulders and his forearms to control an opponent." It added: "Heaven knows, Chàvez is aggressive enough, but the fury is tight, controlled. He still gets hit, but seldom solidly, as Rosario, a fine puncher, discovered."

JC Superstar

When Chávez came home to Culiacán, according to Sports Illustrated, there was a traffic jam more than a mile long on the airport road of fans who wanted to greet him. In February 1988 the Boxing Writers of America named him Fighter of the Year. He was JC, JC Superstar, El César del Boxeo. By then his family lived in a little house on the busy Via Zapata in Culiacán.

"If I was from the United States, maybe I'd be more famous than Mike Tyson," he said that April. "I'm famous in Mexico, that's what I wanted first; to be known and respected in my country."

In October 1988 he beat his friend José Luis Ramírez in Las Vegas to unify the WBA and WBC lightweight titles. On 13 May 1989 he moved up again and took the WBC light-welterweight title from Roger Mayweather, who retired after ten rounds. He had still not lost.