ZZ Top‘s 1972 sophomore album ‘Rio Grande Mud’ turns 40 this month. The album is best known as home to the longtime concert favorite ‘Just Got Paid,’ which features a particularly thrilling slide guitar showcase from Billy Gibbons.

‘ZZ Top’s First Album’ — yes, that’s what they called it — hadn’t made much of an impression on the charts when it came out the year before, but ‘Mud”s lead track, ‘Francine,’ which featured vocals from bassist Dusty Hill, made a bit of a dent, becoming their first charting single. (Things would really bust open for the group with 1973′s ‘Tres Hombres.’

A vintage advertisement for the album declares that the band’s reputation “has literally exploded throughout the South and Southwest,” and a Rolling Stone review written shortly after the album’s release seems to agree the trio is worthy of bigger things, stating that ZZ Top “churns out sizzling electrical blues in a style not far removed from John Mayall’s original Bluesbreakers and early Fleetwood Mac” and promising, “With wider airplay and a little promotion, ZZ Top could, indeed, reach the top.” (Good call!)

With a title that trumpeted both their Texas pride and love of all things south of the border, ‘Rio Grande Mud’ finds the band sounding more full-bodied and confident in the studio than on their initial effort — which is still pretty damn good, by the way! Throughout ‘Mud”s 10 songs, Hill and drummer Frank Beard provide a supple, rock solid and blues-heavy foundation for Gibbons’ vocals and frequently stunning guitar excursions.

The frontman also proves himself quite a harmonica player, delivering gloriously unhinged work that contrasts perfectly with the rest of the traditional “she done me wrong” lament ‘Mushmouth Shoutin’.’ Another highlight is the glacially-paced weeper ‘Sure Got Cold After the Rain Fell,’ which is absolutely the best song in the world to play over and over again at three in the morning after you’ve lost your baby.

For a long time, ‘Rio Grande Mud’ was difficult to find in its original form. The dawn of the CD era coincided with the smash hit success of the band’s synthesizer-heavy ‘Eliminator’ album, and ‘Mud’ was remixed to sound more like that album, or we guess “modern,” and made available in the format only as part of a ‘Six Pack’ collection for a long time. However, you can buy the original version on vinyl now, thanks to those saints over at Rhino Records.

Watch ZZ Top Perform ‘Just Got Paid’