NEW YORK — Katie Taylor retained her undisputed lightweight world championship on Saturday, with a split-decision victory over Amanda Serrano on a historic night in Madison Square Garden in front of a raucous sellout crowd. The Irishwoman, who stretched her unbeaten professional record to 21-0, and Serrano were the first women to headline a fight at the world’s most famous arena and put on a show-stopping performance equal to the occasion. Competing under the watchful eye of pioneering Hall of Famer Christy Martin in the biggest fight in the history of women’s boxing, the meeting between the two best pound-for-pound boxers ushered in a new era for the sport. Promoter Matchroom Boxing said the fight attracted more media applications than Briton Anthony Joshua’s heavyweight fights at Wembley against Wladimir Klitschko and against Oleksandr Usyk at Tottenham Hotspur Stadium. With the Empire State Building lit up in the colors of the Irish and Puerto Rican flags, Taylor secured the seven-figure purse and seemed ready for more. “Let’s do it again, Amanda!” she declared. — Reuters