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Mexican-born guitarist Carlos Santana (right) and bassist David Brown perform with the group Santana at the Woodstock Music Festival in Bethel, New York.

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Fans sitting on top of a painted bus during the Woodstock Music And Arts Festival.

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A man walking past a car notices the feet sticking out of the window during the Woodstock Music And Arts Festival.

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Fans climb scaffolding during the Woodstock Music And Arts Festival.

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The crowd at the during the Woodstock Music And Arts Festival in Bethal, New York in August 1969.

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Hundreds of rock music fans jam highway leading from Bethel, New York, Aug. 16, 1969 as they try to leave the Woodstock Music and Art Festival. Two hundred thousand persons spent a rainy night at the festival.

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Rock music fans sit on a tree sculpture as one leaps mid-air onto a pile of hay during the Woodstock Music and Art Festival held on a cow pasture at White Lake in Bethel, New York on Aug. 15, 1969.

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A mud-caked music lover lies atop his motorcycle at the Woodstock Music and Arts Festival, Aug. 14, 1969.

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About 400,000 people attend the Woodstock Music and Arts Festival in Bethel, N.Y., August 16, 1969.

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This is an aerial photo of the Woodstock Music and Arts Festival held on 600 acres of cow pasture leased from a farmer at White Lake in Bethel, Sullivan County, N.Y., in Aug. 1969. The festival, billed as "Thee Days of Peace and Music," started on Friday, Aug. 15 and ended Monday morning, Aug. 18. More than 450,000 persons attended.

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Rock music fans sit on a tree sculpture as one leaps mid-air onto a pile of hay during the Woodstock Music and Art Festival held on a cow pasture at White Lake in Bethel, New York on Aug. 15, 1969.

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Rock music fans hike from the Woodstock Music and Art Festival in Bethel, New York, Aug. 17, 1969. Some 300,000 fans began to leave as the festival ended in the rain.

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Woodstock Music and Art Festival participants leave the festival on Aug. 17, 1969 in Bethel, N.Y.

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Concert-goers sit on the roof of a Volkswagen bus at the Woodstock Music and Arts Fair at Bethel, N.Y., in mid-August 1969. The three-day concert attracted hundreds of thousands of people, and became a landmark cultural event of the late ’60s.

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Rock music fans relax during a break in the entertainment at the Woodstock Music and Arts Fair in Bethel, N.Y., on Aug. 16, 1969.

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Young people abandon their trucks, cars and buses as some 200,000 persons try to reach the Woodstock Music and Art Festival on a leased cow pasture at White Lake in Bethel, New York Friday, Aug. 15, 1969. Cars were backed up for 10 miles. The festival closed the New York State Thruway, creating the nation?s worst traffic jam.

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Grass and leaf huts are used as makeshift living quarters for some of the attendees at the Woodstock Music and Arts Festival at White Lake in Bethel, N.Y., in Aug. 16, 1969. The festival, billed as "Three Days of Peace and Music," took place Aug. 15-18.

AP

Hundreds of rock music fans jam highway leading from Bethel, New York, Aug. 16, 1969 as they try to leave the Woodstock Music and Art Festival. Two hundred thousand persons spent a rainy night at the festival.