Las Vegas 51s

In 2001, Las Vegas became the top farm club of the Los Angeles Dodgers. The new affiliation was accompanied by rebranding to the Las Vegas 51s in reference to Area 51, a military base located north-northwest of Las Vegas legendary for rumors of its housing UFOs and other extraterrestrial technology. The team adopted a logo featuring a grey alien head and introduced an extraterrestrial mascot named Cosmo.

A new affiliate, moniker, and appearance did not translate into improved performance on the field. The 51s experienced only two winning seasons during their eight years as the Triple-A Dodgers. Their only division title came under manager Brad Mills in 2002 as the team posted the best record in the league at 85–59, but lost three games to one to the eventual PCL champion Edmonton Trappers.

On March 24, 2008, Mandalay Baseball Properties sold the 51s franchise to Stevens Baseball Group. There were no plans to move the team, and talks of building a new stadium to replace the ageing Cashman Field became stagnant. The Dodgers and the 51s had a rocky relationship during their eight-year affiliation. The Dodgers were not pleased with Cashman Field, which barely met the standards for Triple-A baseball. It had no weight room or indoor batting cages, and it was decrepit compared to other stadiums in the league. Citing the inadequacies of Cashman and lack of planning for a replacement, Los Angeles decided not to renew their player development contract (PDC) with Las Vegas after the 2008 season.

Following the departure of the Los Angeles Dodgers, the 51s signed a PDC with the Toronto Blue Jays, marking the first time that the 51s were affiliated with an American League club. The only time the team finished over .500 with the Blue Jays was in 2012 when Marty Brown led the team to a 79–64 second-place finish. The Blue Jays ended their affiliation with the 51s after the season.

In April 2013, the team was purchased by Summerlin Las Vegas Baseball Club LLC, a joint venture of Howard Hughes Corp and Play Ball Owners Group, including investors Steve Mack, Bart Wear, and Chris Kaempfer, with intentions of moving it to a proposed stadium in Summerlin near the Red Rock Resort Spa and Casino.

The 51s became affiliated with the New York Mets in 2013 when they were the only Triple-A team left without a MLB parent. They won back-to-back division titles in 2013 and 2014 under manager Wally Backman, but were eliminated in the Pacific Conference championship series on both occasions.

In 2017 the 51s became one of the first teams to participate in the Copa de la Diversión initiative and for selected games played as the Reyes de Plata ("Silver Kings"). The name was a nod to Nevada being the "Silver State" and a homage to the contribution migrant workers made to the mining industry of Nevada.

In October 2017, the Las Vegas Convention and Visitors Authority approved a 20-year, $80 million naming rights agreement to help pay for the new $150 million 10,000-seat ballpark which opened in 2019. Las Vegas Ballpark, located in Summerlin, is includes 22 suites, a center field pool, kids' zone, and several bars. Construction began in 2018 and was completed for the 2019 season.

In late 2017, the Mets announced plans to move its Triple-A affiliation to the Syracuse Mets beginning in 2019, meaning the 51s would be in need of a new major league affiliate.