Forty-three years ago today (June 8, 1974) was an historic day for Dolly Parton: It was on that date that the country legend landed at the top of the charts with her song "I Will Always Love You," from her Jolene album.

Chances are, Parton had no idea how monumental "I Will Always Love You" would become when she wrote it. The song, which became one of the biggest hits of Parton's career, was written to her one-time mentor, Porter Wagoner, when she decided to end her professional partnership with him and launch out on her own.

“It’s saying, ‘Just because I’m going don’t mean I won’t love you,'" Parton explains. "'I appreciate you, and I hope you do great, and I appreciate everything you’ve done, but I’m out of here.'"

While Parton and Wagoner remained estranged for much of their careers following their professional split, they made up before Wagoner's death in 2007. Parton sang "I Will Always Love You" for Wagoner at a special ceremony at the Grand Ole Opry only a few months before he passed away.

"It was the most emotional night that I've ever spent at the Opry in my whole life," Wagoner told Yahoo! Music. "And Dolly, of course, sang that song, "I Will Always Love You," and they had me sitting on a stool, and she just came out and wiped some of the tears away ... She meant it for me and wrote it for me, she said. That's a wonderful thing that she stood there and sang it for the whole world to see. And the evening was unbelievable."

"I Will Always Love You" is also featured on the soundtrack for 1982's The Best Little Whorehouse in Texas, in which Parton stars, along with Burt Reynolds. At the time of the movie's debut, the song returned to the top position on the charts, making Parton the first artist to earn a No. 1 record twice with the same song and same singer.

Parton also recorded "I Will Always Love You" with Vince Gill in 1995, for his greatest hits album Souvenirs. Even though their version wasn't officially released as a single, it peaked at No. 15 on the Billboard charts; they also sang it at the 1995 CMA Awards.

"I Will Always Love You" has been covered by numerous artists, including Linda Ronstadt, LeAnn Rimes and Lulu Roman, but it was Whitney Houston's version, in 1992, for the film The Bodyguard, that introduced the anthemic love song to an entirely new audience. Houston's version also soared to the top of the charts, where it stayed for a record-breaking 14 weeks. However, "I Will Always Love You" almost became a hit for another big star: Elvis Presley. The King of Rock and Roll wanted to record it, but Parton refused after Presley's manager, Col. Tom Parker, insisted that Presley receive half of the publishing royalties on the song.

"I Will Always Love You" remains one of the best-selling songs of all time. It is available for download on iTunes.

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