Led Zeppelin gave a last-minute concert at a Wheaton rec center on the night of President Nixon’s inauguration. Or did they? Filmmaker Jeff Kulik tries to separate fact from rock-and-roll myth in “Led Zeppelin Played Here.” (DICK BARNATT/REDFERNS)

Some questions are cloaked in the mists of prehistory. Who built Stonehenge? Why did the Mayan civilization collapse? Did Led Zeppelin perform at the Wheaton Youth Center on Jan. 20, 1969?

That last mystery might seem the easiest to solve. There are, after all, people who claim to have attended the concert. Several of them make their case in “Led Zeppelin Played Here,” an entertaining if inconclusive documentary by local filmmaker Jeff Krulik, who’s probably best known for 1986’s “Heavy Metal Parking Lot.”

“I never found one shred of evidence” to document the alleged show, reports local pop-culture historian Mark Opsasnick in the movie. There are no posters, no ticket stubs, no photographs, no newspaper accounts. Just a whole lotta confusion.

The show, says co-promoter and former DJ Barry Richards, was scheduled at the last minute and publicized mostly on his own radio show on WHMC. That low-power station’s signal didn’t travel far outside Montgomery County, so rock fans in Alexandria, Upper Marlboro or Capitol Hill wouldn’t have heard about the concert.

Those who say the performance did happen offer colorful details: It was Zeppelin’s smallest audience ever, only about 50 people. And the band’s lowest-paying gig ever, supposedly. The future chart-toppers might even have played as the New Yardbirds, the working name for the group in its formative days.

For Krulik, the point is the journey, not the destination. And that journey goes in a half-dozen amusing directions. The movie is an investigation of sorts, but also a collagelike evocation of the period, and of hard rock before it became big business. (Before the band left Wheaton, some say, its manager demanded gas money.)

The date of the alleged concert was also Richard M. Nixon’s first inauguration as president, so that event briefly becomes the documentary’s focus. Then there’s a condensed history of local concert promotion, circa 1969, that visits various local teen centers.

In the process, the movie discovers conflicting memories about many little-documented rock shows of the period. That leads to the definition of confabulation: when people tell untruths they absolutely believe to be true.

Ultimately, the surviving members of Zeppelin just happen to fall into Krulik’s benign clutches. But that settles nothing.

If the sound and video quality are a little rough, that suits the raw material, which includes amateur 8-mm film and Instamatic photos. Wittily assembled, “Led Zeppelin Played Here” develops a conversational tone that’s lively and effective. The movie is one of those stories of rock war veterans that’s great fun to hear, even if you don’t buy a word of it.

Jenkins is a freelance writer.

★ ★ ★

Unrated. At AFI Silver Theatre. Contains brief profanity and references to drug use. 81 minutes.