Vonn's win is the first by an American woman since 1983

American Lindsey Vonn sealed her first overall World Cup title on Friday by taking an unassailable lead following the season's final slalom in Bormio.

The 23-year-old has joined compatriot Bode Miller as overall champion, the first time the USA has won both the men's and women's titles since 1983.

"It's been an amazing season," said Vonn, formerly known as Lindsey Kildow.

Austria's Marlies Schild retained her World Cup slalom title, while American Ted Ligety won the men's giant slalom.

Schild led after the first run and, despite coming under pressure, she held on to her lead in the second run with an overall time of one minute 52.78.

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Her team-mate Nicole Hosp finished second overall in the slalom and Slovakia's Veronika Zuzulova snatched third.

Vonn had already won the downhill title and her overall triumph is the first by an American women since Tamara McKinney in 1983.

She lagged behind in 25th place after the first run, but fought back with the fastest second run to finish 11th on the day, more than enough for the overall title.

Miller wrapped up his second overall World Cup on Thursday after Swiss Didier Cuche, the only man who could catch him, opted not to race in Saturday's final slalom.