When Van Halen were on their way up in the late '70s, there was no such thing as YouTube or social media. If you wanted to make it big, you had to earn your fanbase one screaming crowd at a time -- and in the summer of '78, the band took the stage in front of one of the biggest audiences of its young career.

That moment is captured in the above clip from the new documentary 'Texxas Jam '78,' which takes a look at the behind-the-scenes story of the titular festival, a rock extravaganza that unfolded over the July 4 weekend in front of 80,000 sweaty concertgoers and featured performances from a star-studded bill that included Aerosmith, Ted Nugent, Heart, Journey, and Eddie Money.

Among those more established stars strutted Van Halen, who -- as you'll see in the interview segments contained in this clip -- were still mostly an unknown quantity to most of the musicians in the lineup, not to mention many of the ticketholders in attendance. What happened next proved a pivotal moment in the band's early success, and Texxas Jam's subsequent notoriety helped start a new era of rock festivals in the region.

Check it all out in the clip above, and for more information and to purchase the entire movie, visit the film's official website.

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