Portland Hearts of Pine

On September 7, 2023, the United Soccer League announced that the city of Portland, Maine, had been awarded a USL League One expansion team which would start play in the 2025 season. Gabe Hoffman-Johnson, a former soccer player at Dartmouth College and a standout at nearby Falmouth High School, was announced as the club founder, with the ownership group including local real-estate developers Jonathan and Catherine Culley and NESN broadcaster Tom Caron, a native of Lewiston, Maine.

On April 22, 2024, Kevin Schohl, a former vice president at DraftKings and former executive with AMB Sports and Entertainment, the owner of Major League Soccer club Atlanta United FC, was hired as president and chief business officer.

On September 19, 2024, the team announced that a League One-record 96% of its season ticket deposits had been purchased.

The club named St. Louis City 2 coach Bobby Murphy the team's inaugural head coach and sporting director on November 14, 2024. The club's first player, Trinidadian midfielder Michel Poon-Angeron, was signed on December 17, 2024. The club signed Maine native and Lewiston High School alumnus Khalid Hersi on January 8, 2025.

The team's mascot is Moxie the Moose, a nod to the soft drink Moxie, the official soft drink of Maine since 2005.

The club played its first ever competitive match, a 4–0 victory over CD Faialense of the Bay State Soccer League in the U.S. Open Cup, on March 20, 2025. The club's first ever goal was scored in the 18th minute by Walter Varela. The match was played at Lewiston High School's Don Roux Field due to ongoing renovations at Fitzpatrick Stadium. A second U.S. Open Cup match was played at Lewiston High School against USL Championship team Hartford Athletic on April 2. After ending regulation time scoreless, the Hearts were reduced to ten men after an Azaad Liadi red card in the 96th minute, and went down 1–0 to a 107th minute Hartford goal through Jordan Scarlett. In the 117th minute, Jake Keegan equalized for the Hearts, sending the match to a penalty shoot-out. The Hearts converted all four penalties while Hartford missed two, sending the Hearts through to the third round of the Open Cup in an upset. They were eliminated in the following round after a 2–1 defeat to Rhode Island FC, again held at Lewiston High School.

The team's first league match was a 0–0 draw on the road against fellow expansion team FC Naples on March 29, 2025. Over 200 Hearts of Pine fans travelled to Naples for the match. After another 0–0 draw at Spokane Velocity, the club's first goal in league play was scored by captain Patrick Langlois in the club's third league match, a 2–1 defeat to Tormenta FC in Statesboro, Georgia.

On April 30, the Hearts of Pine announced that they had sold out their inaugural match at Fitzpatrick Stadium. The match, played on May 4 and attended by Governor Janet Mills, was a 1–1 draw for the Hearts of Pine against One Knoxville SC. Knoxville's Stuart Ritchie scored the first goal at Fitzpatrick Stadium in the second minute, while Masashi Wada scored the first Hearts of Pine goal at Fitzpatrick in first half stoppage time. Two weeks later, the Hearts of Pine celebrated their first League One victory, a 2–1 win over FC Naples at Fitzpatrick Stadium. The club earned its first road victory in the early hours of July 13, defeating fellow expansion side Texoma FC 1–0 after multiple weather delays.

The club's identity and marketing tactics received praise, with an article in describing the club as "the buzziest" in American soccer. Ad Age also reported that the Hearts of Pine had sold more merchandise than every other team in USL League One combined, and that the club projected to top League One in gross revenue and ticket sales at the conclusion of the 2025 season.