Country music legend Merle Haggard has died on his birthday.

The singer-guitarist, who last performed in Atlanta in August 2015 at Buckhead Theatre and was slated for a May 20 show at Chastain Park Amphitheatre with Willie Nelson, was 79.

One of the original “outlaw country” artists, the California native known as “Hag” brought an enduring gruffness to politically tinged songs including "Okie From Muskogee", "The Fightin' Side of Me", and "I Wonder If They Think of Me,” just a handful of the 38 No. 1 hits he produced throughout his 50-year career.

In December, Haggard was treated at a California hospital for pneumonia, which he suffered from again in March. His April concerts had been canceled because of a battle with double pneumonia.

Among his many accolades, Haggard received a lifetime achievement award at the 2010 Kennedy Center Honors and in 2014 he performed “Okie…” with Kris Kristofferson, Blake Shelton and Nelson at the Grammy Awards.

On Wednesday, Recording Academy president Neil Portnow said in a statement, "Merle’s massive success was rooted in his masterful ability to celebrate the outlaws and the underdogs... his remarkable performances will forever live on and inspire music creators worldwide. We have lost an innovative member of the music community."

Haggard released his last solo album, “Working In Tennessee” in 2011 and last summer collaborated with Nelson on the duet album, “Django & Jimmie.”

“He was my brother. My friend. I will miss him,” Nelson said in a statement from his publicist.

Upon news of his death, country artists ranging from Jason Aldean to Jason Isbell hit Twitter to express their condolences at the loss of the country music giant.

Here is our photo gallery from Haggard’s last Atlanta performance.