In 1968, Houston Freeburg became addicted. He just didn’t know it at the time. His compulsion for collecting rock ’n’ roll concert posters emerged full-blown decades later as both a remembrance of music past and a valuable hobby. In June, he’ll share his passion when 150 of his posters go on display for the exhibit “The Psychedelic ’60s: Posters From the Rock Era” at the Toledo Museum of Art.

Freeburg’s fascination with rock concert posters took off at age 14. A twentysomething teacher at his conservative private boys school in Memphis decided to take 40 kids to New York City for a few days. “I asked my parents and they weren’t concerned. They thought it was my own thing. The teacher brought us there and turned us loose,” says Freeburg. “It was a different time.”

The mandatory events were a teenage dream: Go to a performance of the musical Hair and attend a Procol Harum concert at the Fillmore East. During the trip, Freeburg bought a few black-light posters to go with those in his bedroom, and one of rock god Jimi Hendrix.

In 2004, Freeburg remembered the posters and searched his parents’ house for them. But like many other boomers, who had possessed once-cherished comic books, Barbies and baseball cards, he found that his treasures were gone. So he went on eBay and discovered a time machine that took him back to the posters of his youth. It had “all the ones I had as a kid and more, and I couldn’t help but notice how exorbitant the prices were.”

Undeterred, he bought one, then another, and another, as well as books that taught him which posters were the most valuable. Seven hundred fifty concert posters and 500 black light posters later, Freeburg, 56, has a stellar collection that captures the period’s psychedelic, creative chaos and countercultural ethos, and evokes its pulsating dance floors, drugs, sex and rock ’n’ roll vibe.

Today’s priciest concert posters are from the first printing. It was usually a minimum run of from 250 to 1,000 in a given city. They were nailed on telephone poles or displayed in head shops, and fans spread the music news. The second printing was sold during the show or to collectors afterward. Many of the first printings were destroyed by weather or by moms who tossed them out.

As a consequence, Freeburg says, a lot of those early posters are worth thousands of dollars. He won’t divulge how much he pays or the value of his collection but says, “I have a lot invested in these things, and the spike in value for ’60s posters is diagonally up from left to right.”

His collection is shelved flat in acid-free artist portfolios in a climate-controlled studio. They are labeled sequentially from their printing, and he buys duplicates of rare posters when he can.

Freeburg’s relationship with poster collecting is complicated. He denies it’s an obsession. Instead, he considers buying them as akin to investing in a mutual fund, but a tangible one. He says he won’t buy a poster without considering its financial value. Then again, he admits he has offers to sell posters but can’t part with a single one. “I am sentimental for that time period. I loved about 90 percent of those bands and I feel gifted for having their posters. I would have them all over the house, if my wife would let me,” he says. Neither Freeburg’s wife nor his 21-year-old daughter is a collector.