(CNN) -- Country music legend Merle Haggard, best known for such patriotic hits as "Okie From Muskogee" and "The Fightin' Side of Me," died Wednesday, his birthday, at his home in Northern California. He was 79.
Haggard died of complications from pneumonia, his agent Lance Roberts told CNN.
Haggard recorded more than three dozen No. 1 country hits in a musical career that spanned six decades, from the 1960s into the 2010s. He overcame an early life of crime and a prison term in San Quentin to develop a rugged, outlaw image that helped sell millions of records.
Tributes immediately began pouring in from the country music world and beyond.
"Country music has suffered one of the greatest losses it will ever experience," said country star Charlie Daniels on Twitter. "Rest in peace Merle Haggard."
"Love and prayers for the Haggard family. Merle was a pioneer...a true entertainer...a legend," added Carrie Underwood. "There will never be another like him."
"There are no words to describe the loss & sorrow felt within all of music with the passing of Merle Haggard. Thank God for his life & songs," said singer Brad Paisley.
Despite his advancing age Haggard maintained a robust touring schedule in recent years and had been scheduled to perform Thursday night in Missouri.
Merle Ronald Haggard was born in 1937 near Bakersfield, California. His father worked as a carpenter for the Santa Fe Railroad and the family lived in an old boxcar that they converted into a home.