Boise

Boise was named a potential market for a United Soccer League team in the 2010s amid several friendlies and other matches that showed local interest. Jeff Eiseman, the owner of the minor-league Boise Hawks baseball team, stated that negotiations had been underway for several years with the league but never established franchise rights with the USL. A friendly match between La Liga club Athletic Bilbao and Liga MX club Tijuana in July 2015 drew an attendance of 21,948 at Albertsons Stadium, the football stadium used by the Boise State Broncos. A 2016 USL Championship match between Portland Timbers 2 and the Swope Park Rangers was watched by a sold-out crowd of 4,352 spectators at Rocky Mountain High School in Meridian, Idaho.

The "Boise Sports Park" proposal, which never came to fruition, was to build a multi-use baseball and soccer stadium for the Boise Hawks and a new USL team was announced in 2017. The stadium near downtown Boise would have had a capacity of 7,000 to 8,000 for soccer matches and use a turf pitch. The Boise Hawks' ownership group, Agon Sports & Entertainment, announced in January 2019 that it had signed a franchise agreement with USL to field a USL Championship team in Boise once the stadium was completed. The stadium was planned to be completed by 2021 if funding from a public development corporation was in place. The original proposed site for the Boise Sports Park drew opposition from local residents and was replaced by a new location in the West End neighborhood, but a voter-approved ordinance to require a citywide election on any sports stadium with public funding and financing issues led to the project being shelved in December 2019.

USL officially announced the expansion team under the working name Boise Pro Soccer on October 30, 2024. The ownership group included former National Basketball Association executive Brad Stith, real estate developer David Wali, former U.S. Soccer Federation executive Bill Taylor, and stadium developer Steve Patterson. Former U.S. national team goalkeeper and commentator Kasey Keller joined the ownership group in July 2025. Nate Miller was announced as head coach in October 2025. AC Boise announced the signing of their first player, former MLS defender Blake Bodily, on January 6, 2026.

The team won their first regular season match, on the road to fellow expansion team Sarasota Paradise, 1–0 on March 7, 2026. Midfielder Denys Kostyshyn scored the first goal in Athletic Club Boise history. The first home match was a 1–1 draw with Spokane Velocity FC that had 7,211 spectators—setting a league record. The team sold out their first nine home matches and set a single-match league attendance record of 7,247 spectators on June 20 against Union Omaha. On September 9, 2026, AC Boise announced that the men's team would join the USL Championship for the 2027 season, becoming a second-tier team. A new grandstand at the existing stadium would bring capacity to 10,000 spectators as part of the requirements for the new league. The women's team was originally planned to debut in 2027, but was delayed to the following year after the USL Super League changed to a new schedule format.