The Eagles scored a massive success with their final studio album in 2007, boosted by the success of its second single, "How Long." Though the recording was new, the song had actually been part of the band's history since nearly its inception in the early 1970s.

Longtime Eagles co-writer J.D. Souther wrote "How Long," and he included it on his debut solo album, John David Souther, in 1972 — the same year Glenn Frey, Souther's former partner in a duo called Longbranch Pennywhistle, released his first album with the Eagles.

Souther would go on to co-write Eagles classics including "Best of My Love," "New Kid in Town," "Heartache Tonight" and more, and the Eagles included "How Long" in their live sets in the early and mid-'70s.

The band reunited unexpectedly in 1994, and began working on a new studio album a few years later after several very successful tours. The album took six years to record, and in the end, Long Road Out of Eden was a double album comprising 20 tracks.

"How Long" came closest to replicating the group's classic blend of rock and country, and it scored a solid hit after its release on Aug. 16, 2007, hitting No. 23 on Billboard's Hot Country Songs chart, No. 7 on Adult Contemporary and No. 1 on the Bubbling Under Hot 100 Singles chart.

The song went on to win the Eagles a Grammy Award for Best Country Performance by a Duo or Group With Vocal, and another track from the album, "I Dreamed There Was No War," won a Grammy for Best Pop Instrumental Performance.

Long Road Out of Eden scored a massive success upon its release in November of 2007, both commercially and critically. The album reached No. 1 on Billboard's Top Country Albums chart on Nov. 17, 2007, and it also led the Top Rock Albums chart, as well as the all-genre Billboard 200. The project also charted in countries all over the world, and it spawned no fewer than five hit singles, with "No More Cloudy Days," "Busy Being Fabulous," "What Do I Do With My Heart" and "I Don't Want to Hear Anymore" all joining "How Long" as singles from the project.

The album stands as the band's final studio project. Glenn Frey died in 2016, and in 2017, his son Deacon and Vince Gill joined the Eagles' touring lineup, which has continued to perform off and on ever since.

The Eagles announced their final tour, The Long Goodbye, in June of 2023. The massive trek will likely continue into 2024 and 2025 as the band says goodbye to its fans by playing as many shows in every city as fans demand.

PICTURES: See Inside Glenn Frey's Sprawling California Mansion

Eagles founder Glenn Frey lived the good life. The legendary singer and guitarist and his wife lived in a 6-bedroom, 9-bathroom, 9,000-square-foot Spanish mansion in a very high-dollar area of Los Angeles, which sold for $14 million after Frey's death in January of 2016.

PICTURES: Look Inside Don Henley's New $4.3 Million 'Green' Home in California

Eagles leader Don Henley recently purchased a luxurious home in California for his son, and the 4-bedroom, 4.5-bathroom, 3,554-square-foot home is compatible with his environmental activism.

More From KIKN-FM / Kickin' Country 99.1/100.5