An American Treasure, the first posthumous Tom Petty project, is designed as an aural biography of the late rocker, telling a tale that begins with a Mudcrutch session from 1974, running through the glory of Tom Petty & the Heartbreakers in 1976, and concluding with a live version of "Hungry No More" from 2016, just over a year prior to his tragic 2017 passing. Arriving roughly a year after Petty's death, the timing for An American Treasure makes sense -- he certainly deserved a tribute -- but in strict discographical terms, there didn't seem to be a need for a second career-spanning box set, as he already had 1995's rarity-laden box Playback and a multi-disc The Live Anthology from 2009. Happily, An American Treasure offers a story that's not told on either previous set, and that's a complete picture of Petty's career, told entirely through byways, not highways. The compilers -- a team consisting of his widow Dana, daughter Adria, bandmates Mike Campbell and Benmont Tench, plus longtime producer Ryan Ulyate -- made a conscious decision not to replicate any material from Playback, which meant that there wasn't room for the original hit versions of any of Petty's hits. Ultimately, this meant that many of his best-known songs are nowhere to be found on An American Treasure, but that winds up as a feature, not a bug. In the absence of "American Girl," "Refugee," "The Waiting," and "Free Falling," the spotlight shifts to the remarkable consistency of Tom Petty's catalog, which is represented through deep cuts, alternate takes, live versions, and unheard songs. Upon first glance at the track listing, it may seem like there's not a treasure trove of unheard material, but as An American Treasure plays, what becomes clear is that the bigger picture counts more than the individual details. Not that the box doesn't serve up some unexpected surprises from all eras: an alternate "Rebels" has a muscle lacking on the original version, Echo generates two fine rarities in "Gainesville" and "I Don't Belong," the plaintive outtake "Don't Fade on Me" could've fit onto Wildflowers with no problem. It's fun to cherry-pick these tracks, but An American Treasure carries a greater resonance by demonstrating how Petty kept growing through the years, not only as a songwriter but a performer; some of the best moments are hearing him sing older songs later in his career. The trick An American Treasure pulls off is weaving these latter-day performances into the place where the songs were originally written, so this not only provides a narrative but also gives a sense of continuity, which is a rare thing in a decades-spanning box like this. As such, this box winds up as a fitting tribute to a rocker whose touch was so casual, he could be easy to take for granted, but when his work is looked at as a whole, he seems like a giant.