"We were on our way to Jacksonville and decided to stop in Ft. Walton Beach tonight! Come party with us! 9:30 at The Block!" she tweeted with a photo of the venue.

According to CMT, Lambert's Airstream arrived at the venue at 2 p.m. and fans soon lined up around the block for the show. The 700-capacity venue was quickly filled for Lambert's free two-hour concert.

In addition to her hits, "Fastest Girl in Town," "Even Prettier," "Over You," "Heart Like Mine" and "Gunpowder & Lead," Lambert took a break from the mic to play cowbell and let some of her band take part as frontwoman, bandmate Carolyn Dawn Johnson taking the reins on Bryan Adams' 1984 hit, "Summer of '69."