MADRID -- American Christopher Horner is getting the best results of his life at an age when most cyclists have already retired.

The 41-year-old veteran completed the biggest victory of his career on Sunday, becoming the first American to win the Spanish Vuelta and the oldest champion of one of cycling's three-week grand tours.

American Christopher Horner, 41, rode into Madrid with his RadioShack-Leopard teammates Sunday after effectively clinching the race over the last three days. AP Photo/Paul White

"I've been a professional for almost 20 years, so this represents a lifetime of hard work," Horner said. "A grand tour is always a goal for a cyclist to show how good of a rider you are. The memories will last forever."

Horner navigated the final flat stage without mishap to arrive in Madrid together with his RadioShack-Leopard teammates after effectively clinching the race in the northern mountains over the last three days.

Vincenzo Nibali of Italy and Spaniard Alejandro Valverde -- both former winners -- were second and third, respectively.

The previous oldest winner for one of the three grand tours -- the Vuelta, Tour de France and Giro d'Italia -- was Fermin Lambot, who won the 1922 Tour at 36.

"Many riders winning in their 20s and early 30s have small children, but mine are at the age where they can appreciate what dad is doing," Horner said. "When I get back, it will be quite the topic at home."

Horner, who will turn 42 next month, beat nearest challenger Nibali by finishing ahead of the Italian in each of the final three mountainous stages before Sunday's 68-mile ride from Leganes to Madrid.

Michael Matthews of Australia won the 21st and final stage in a sprint through Madrid's city center.

"We only had four other teammates to help with the sprint today, but everyone did their job 100 percent to help me get the win," Matthews said after his second stage win at this Vuelta for Orica Greenedge.

The 68th Vuelta was geared to favor strong climbers, with 13 of its 21 stages set in the mountains.

And Horner made the most of it, consistently pulling away with his high riding stance and a wry smile on his face while his younger rivals agonized behind him.

"I loved this course. When I first saw the design, I knew it was perfect for me and my style of racing," Horner said.

He was not among the favorites entering the race, but Horner quickly joined them upon winning the third stage. That made him the oldest rider to win a stage at a grand tour, breaking the former record held by Pino Cerami, who won a Tour stage at 41 years, 2 months.

In the decisive stage Saturday, Horner resisted Nibali's repeated attacks before leaving him behind in the fog as he surged up the Alto de L'Angliru peak, increasing his lead from 3 to 37 seconds.

"Yesterday you saw how much effort Nibali put in to try to win this race," Horner said. "It was no walk in the park for me. It was probably the hardest victory I've ever had in my career and possibly the hardest race I've had in my career."

Horner completed the grand tour in 84 hours, 36 minutes, 4 seconds. Nibali remained 37 seconds behind, followed by Valverde 1:36 back.

Horner turned professional in 1995. His previous wins included the Tour of Georgia in 2003, the Tour of the Basque Country, a northern region on Spain, in 2010, and the Tour of California in 2011.

Euskaltel-Euskadi, the financially troubled Basque team that Formula One driver Fernando Alonso is considering sponsoring, finished as the best team at the race and the only won not have a member retire. The rest of the peloton let Euskaltel-Euskadi ride in front as it entered the city.