With the coronation of her side project, Pistol Annies' "Hell on Heels," Miranda Lambert  is the first artist in the 47-year history of Billboard's Country Albums  chart to have notched No. 1s solo (her first three, 2005-09) and as part of a separately-named, non-all-star group.
(Lambert's own current solo single "Baggage Claim" concurrently jumps 17-13 in its fourth frame on Country Songs and remains the youngest title inside the survey's top 20. The title cut from "Heels" is bubbling under Country Songs, with airplay of the song detected at 18 chart reporters, according to Nielsen BDS).
Considering the highly collaborative habits of country artists, it may at first seem odd that Lambert's chart feat had never before been accomplished.
Coming close was Norah Jones ' country music detour, "The Little Willies," which brought the jazz artist to Country Albums (No. 10) in 2006. (While Jones has thrice topped the Billboard 200 as a soloist, she's never appeared on her own on Country Albums).
Michelle Branch  covered similar ground. The country/pop singer-songwriter scored a Hot Country Songs No. 1, "Leave the Pieces," five years ago this month as half of the Wreckers (with Jessica Harp). Their only release to-date, "Stand Still, Look Pretty," rose to No. 4 on Country Albums. As a soloist, Branch sent her "Everything Comes and Goes" EP to No. 35 last year.
More commonly, when country music's core solo artists fix to team up, it takes the form of a multi-artist superstar duo, trio or group under their own individual names.
Dolly Parton , Linda Ronstadt and Emmylou Harris partnered for "Trio" in 1987 (No. 1 on Country Albums), with a second installment (No. 4) a dozen years later. In 1993, Parton joined Loretta Lynn and Tammy Wynette for their "Honky Tonk Angels" album (No. 6).
Nicknamed "Country's Mt. Rushmore," Willie Nelson , Johnny Cash , Waylon Jennings  and Kris Kristofferson thrilled fans with two volumes of "Highwayman" albums in 1985 (No. 1) and 1990. And, the memorable "Class of '55 (Memphis Rock & Roll Homecoming)" reunited Cash with his iconic Sun Records colleagues Carl Perkins, Jerry Lee Lewis and Roy Orbison. The collection climbed to No. 15 on Country Albums in 1986.
Pistol Annies are cut from a much different bolt of cloth.
Unlike those starpower-packed acts, Lambert is clearly the ringleader of the trio, rounded out by Ashley Monroe and Angaleena Presley. Rather than safely assembling an all-girl supergroup, Lambert's mission was an experimental - and uncertain - one.
The warm reception for "Heels" from fans is likely to both inspire and unsettle some of the label chiefs along Music Row, who attenuate the vast majority of their time and resources gambling on winning bankable stars for country radio and touring. That Lambert's side project came to life in a fairly autonomous way - it formed on April 4, 2011 during the Academy of Country Music's April "Girls' Night Out" special - speaks volumes about the changing business code in Nashville, which has historically cautioned against anything that might detract from a solo artist's momentum.
Just imagine the look on his label president's face when Merle Haggard , at the peak of his career, pitched the idea of recording a live blues album. While Haggard's bosses may have taken a reluctant, white-knuckle ride with Haggard's scheme, the result was an album, "I Love Dixie Blues...so I recorded 'Live' in New Orleans," that spent two weeks at No. 1 on Country Albums in 1973.
It was the same individualistic drive that delivered Nelson's first No. 1 single ("Blue Eyes Crying in the Rain," 1975) from an offbeat concept album that few at his label believed would succeed. The results? "Red Headed Stranger," about a fugitive on the run after killing his wife and her paramour, spent six weeks at No. 1 on Country Albums, 253 total weeks on the chart and was certified double-Platinum by the RIAA.
All that history reinforces that the Pistol Annies' ascent to No. 1 (with a bullet ...) is clearly a rarity in a genre not generally known for breaking from its traditional business model.
Notably, it demonstrates willingness, if not eagerness, on the part of Lambert's team to harness, nurture and profit from the abundant creativity and energy that she possesses and then successfully integrate her side pursuit into her commercial solo career path.
Such icons as Nelson, Haggard and Jennings notoriously had to fight for such artistic freedom.
Perhaps Lambert's lauded leap is an instance of contemporary fulfillment of the promise upon which those old wars were waged long ago.
Wade Jessen is Billboard's Nashville-based senior chart manager for country, bluegrass, Christian and gospel formats
- Chart Beat