Underwood co-wrote this song with Luke Laird and Hillary Lindsey. It's about a drunken flirtation that turns into a Vegas marriage.
Underwood acknowledges that though she has personally never drunkenly eloped to Las Vegas or even been inebriated enough to embarrass herself, this song is inspired by personal experience. She confessed to USA Today October 18, 2007: "I met a guy at an after-party and asked him his last name 3 times, but it never stuck. He got my number, we talked a few times, and I didn't know what his last name was. I was way past the point where I should have known his last name, and if I asked him, I knew it would offend him."
Luke Laird told AOL the story behind this song: "We wrote 'Last Name' in January of 2007. My manager, Chris Oglesby, set up the co-write with Carrie, Hillary Lindsey, and myself. Hillary is one of my best friends, so we had written many songs together. The three of us had already written one song that day. Then Carrie was telling us about meeting some guy at a post-Oscar party. The guy got her number, but when he called her she realized she didn't even know his last name. He called her a couple of times, but she said it was past the point of her asking him his last name. Anyway, when Carrie told us that story, we all just ran with 'last name' and came up with a fun storyline. Very fun day! We laughed a lot."
Lindsey and Laird, together with Underwood, wrote her hit single "So Small" two days prior to this.
Excluding holiday and chart releases, this was Underwood's fourth consecutive #1 on the Hot Country Songs chart. She thus became the first solo female artist to have four chart-toppers in a row on the country survey, since Rosanne Cash
had a string of six #1 titles between 1987-89.
At the 35th People's Choice Awards held on January 7, 2009, this won the award for Best Country Song. Carrie Underwood also came first in the Favorite Female Singer and Star Under 35 Years Old categories.
Underwood performed this at the Grammy Awards in 2009, where the song won the prize for Best Female Country Vocal Performance.
Speaking at the benefit concert We're All for the Hall, Underwood spoke about the story behind the song. "Before I met my beautiful, wonderful, perfect hockey husband [Mike Fisher], I had met this guy," the Country star revealed to the crowd. "I got together with Hillary Lindsey and Luke Laird to write, and we were goofing around like we always do. I was telling them about this guy I met. They asked who he was, and I said, 'Y'all! I don't even know his last name!'"
She continued: "We hadn't even dated or anything and it didn't turn out the way this song did, but I said, 'We need to turn this mess into a song!' And this is it."