Why: For two decades, Merle Haggard was as reliable of a hitmaker as you'll find in country music. The Hag's career has stretched 50 years, and during that time he's charted over three dozen No. 1 songs and become known as one of the true legends of country music's greatest era. Hits like 'Mama Tried,' 'Working Man Blues' and 'Big City' continue to feel as relevant in the 2010s as they did in the '70s and '80s. Faith Hill and Tom T. Hall are superstars, but have nowhere near the resume of Haggard.

Honorable Mentions: Faith Hill, Tom T. Hall and Ferlin Husky.