Allen was born in Milton, Delaware, United States, but moved to Nashville, Tennessee, in 2007. During most of his first few years in Nashville, he experienced poverty and often lived out of his car. Allen auditioned for America's Got Talent, but did not make it past the preliminary auditions. He also auditioned for the tenth season of American Idol, but was cut before the live voting rounds. While on American Idol, he performed with Colton Dixon during one of the group rounds and befriended Scotty McCreery, who eventually won the competition that year. Allen and McCreery later reconnected and toured together after the release of Allen's debut album. Allen signed a publishing deal with Wide Open Music, a songwriting imprint formed by singer-songwriter Ash Bowers, in 2016. After doing a talent showcase for representatives of Broken Bow Records in early 2017, he was signed to that label's Stoney Creek imprint and released his self-titled debut EP, which Bowers produced. The label's executive vice president said that the decision to sign Allen was "one of the fastest they ever made at the label." Stephen Thomas Erlewine of AllMusic compared the EP's sound to the "slick, assured style" of Thomas Rhett and Sam Hunt. Similarly, Rolling Stone Country writer Brittney McKenna compared Allen's contemporary R&B influences to those artists and Maren Morris. A track from the EP, "Blue Jean Baby", was added to Spotify's "United States Viral 50 chart". His first official single, "Best Shot", was released in early 2018. The week of its release, it was the second most-added song to country music radio playlists. The song has made the Hot Country Songs, Country Airplay, and BillboardHot 100 charts and was made into a music video. Allen said that the song's title and central theme were inspired by his grandmother and his son, who was 4 at the time of the song's release. His debut album, Mercury Lane, was issued in October 2018. Also produced by Bowers, the album takes its name from the street on which Allen lived as a child. "Best Shot" was a Number One hit on the Billboard Country Airplay chart in November 2018, making him the first black artist to send his debut single to the top of that chart. The album's second single, "Make Me Want To" released to country radio on February 1, 2019, and it also became a Number One hit on the Billboard Country Airplay chart. Allen also recorded a cover of Lady Gaga and Bradley Cooper's "Shallow" with Abby Anderson in May 2019. The recording was made into a video as well. In 2020, Allen released "This Is Us", a duet with Noah Cyrus. It will be included on his new EP, Bettie James, which will be released on July 10, 2020.
Personal life
Allen has a son from a previous relationship. Allen got engaged to Alexis Gale, 23, his girlfriend, at Disney World on Monday, July 15, 2019. The couple met through Allen’s cousin’s wife, and actually share the same hometown of Milton, Delaware, and began dating the spring of 2019. Allen claims the two "had an instant connection."