As the longest-running music program in TV history, “Austin City Limits” has presented more than its fair share of living legends. But the show also has introduced public television audiences to many future stars in the early stages of their career. Tuesday was that kind of evening at ACL Live, as 24-year-old Lucy Dacus of Richmond, Virginia, made an auspicious debut with a 10-song set that caught this promising singer-songwriter just as she seems to be reaching full bloom.

When greats such as Buddy Guy, the Pretenders or Paul Simon (to cite three from recent seasons) play the show, it’s largely an opportunity for those artists to document their hallmark works against the iconic “ACL” skyline backdrop. With Dacus, we’re watching a career catalog being built right before our eyes. Three of the songs she played Tuesday have surfaced just this year, in the wake of her acclaimed 2016 indie debut “No Burden” and its 2018 follow-up “Historian” on Matador Records.

Dacus began the night noting the absence of her friend Julien Baker, with whom she teamed last year in the trio Boygenius (along with singer-songwriter Phoebe Bridgers). This night was intended to be a dual taping, with Dacus and Baker each doing a set, before an announcement less than three hours before showtime that Baker would not appear because of “unforeseen medical circumstances.” (A ticketed show on Wednesday at the Paramount Theatre featuring both performers was canceled altogether.)

“I just want to say that tonight’s not what I expected it to be,” Dacus lamented at the outset, appealing to the bond of mutual respect between artists and their fans. “Part of that is just to trust that we’re making the right decision,” she said as a lead-in to “Trust,” a song from “No Burden” that she wrote when she was 16 and performed solo acoustic to open the show.

PHOTOS: Austin360 A-List gallery of Lucy Dacus "Austin City Limits" taping

Joined thereafter by her three-piece backing band — guitarist Jacob Blizard, bassist Dominic Angelella and drummer Ricardo Lagomasino — Dacus proceeded through a set that drew from high points on “Historian” and “No Burden” but also played up some of her freshest material. Dacus is midstream on a string of holiday-themed singles in 2019; tunes about Halloween, Thanksgiving and Christmas are still to come, following recently-issued songs that dealt with Mother’s Day and Independence Day.

For “My Mother & I,” Blizard and Angelella both strummed acoustic guitars, with Blizard kneeling and Angelella sitting cross-legged onstage. (When’s the last time you’ve seen that on “Austin City Limits”?) Dacus remained standing at the microphone, tweaking dials on a small effects box to add ethereal synth backing at key moments. The presentation enhanced the desired effect of intimacy for a song that’s instantly one of her best, especially the closing couplet: “All she has given, all I have taken/ All is forgiven, all is forsaken.”

“Forever Half Mast” was her July Fourth song, its title tipping off how Dacus felt on the holiday this year. “We're in a state of disarray, united by our darkest days," she sang. "America, the tried and true, red and white and black and blue/ Tell me, who did this to you? If it was me, I hardly knew.”

Dacus and her band really hit their stride in the closing stretch. “I Don’t Wanna Be Funny Anymore,” the 2015 single that got everything started for her, preceded “Night Shift,” a gloriously emotional rocker that fed off her whirling-dervish bassist's boundless energy. Dacus brought the tone back down for the churchlike “Historians,” the crowd turning reverently quiet for a number that featured only Blizard’s atmospheric guitar and her voice.

Dacus finished just as she started, all alone onstage, though this time with an electric guitar instead of acoustic. Confiding that she’d been intimidated by the prospect of performing on “Austin City Limits,” she said the show’s crew and the crowd had helped put her at ease. Earlier, referencing previous visits to Austin — she’s been here for South by Southwest and the Austin City Limits Music Festival — Dacus had expressed sincere gratitude: “I’ve always felt understood and very at home here.”

That final song, “Fool’s Gold,” hasn’t yet been released, but it confirms Dacus is making the best music of her life right now. With a subtly alluring melody and an urgency to the rhythm that keeps emotions on edge, she walks a tightrope in evocative lyrics that reference having life in a chokehold, where it’s “all glittering fool’s gold.” There’s no pyrite with Dacus. This is the real thing.

WATCH: Austin360's Eric Webb interviews Lucy Dacus at ACL Fest 2016

Listen — Our Austin360 Radio rundown of the 2019 Austin City Limits Music Festival lineup: