The Seattle Mariners are an American professional baseball team based in Seattle. The Mariners compete in Major League Baseball (MLB) as a member club of the American League (AL) West Division. The team joined the American League as an expansion team in 1977, playing their home games in the Kingdome. Since July 1999, the Mariners' home ballpark has been T-Mobile Park, located in the SoDo neighborhood of Seattle. The "Mariners" name originates from the prominence of marine culture in the city of Seattle. They are nicknamed the M's, a title featured in their primary logo from 1987 to 1992. They adopted their current team colors – navy blue, northwest green (teal), and silver – prior to the 1993 season, after having been royal blue and gold since the team's inception; the original colors continue to be used in alternate uniforms. Their mascot is the Mariner Moose. The Mariners did not field a winning team until 1991, and further success eluded them until the late 90s, the most successful period in franchise history. Led by Hall of Fame players Edgar Martínez, Ken Griffey Jr., and Randy Johnson, the Mariners clinched their first playoff berth in 1995 when they won their first division championship and defeated the New York Yankees in the ALDS. Martínez's walk-off double in Game 5 drove Griffey in from first base to win the game in the 11th inning, clinched a series win for the Mariners, served as a powerful impetus to preserve baseball in Seattle, and has since become an iconic moment in team history. They would later win their second division title in 1997. After Griffey, Johnson, and Alex Rodriguez all left the team, the Mariners, bolstered by the signing of Ichiro Suzuki, won 116 games in 2001, which set the American League record for most wins in a single season and tied the 1906 Chicago Cubs for the Major League record for most wins in a single season. The team would not make the postseason again until 2022, which was the longest active drought in the four major North American sports. As of 2024, the franchise has finished with a losing record in 30 of 48 seasons. The Mariners are the only active MLB franchise never to have appeared in the World Series, currently holding the longest active World Series appearance drought in MLB.

T-Mobile Park

The Tampa Bay Rays are an American professional baseball team based in St. Petersburg, Florida. The Rays compete in Major League Baseball (MLB) as a member club of the American League (AL) East division. Since its inception, the team's home venue has been Tropicana Field. Following nearly three decades of unsuccessfully trying to gain an expansion franchise or enticing existing teams to relocate to the Tampa Bay area, an ownership group led by Vince Naimoli was approved on March 9, 1995. The team began play as the Tampa Bay Devil Rays in the 1998 Major League Baseball season. The team's first decade of play was marked by futility; they finished in last place in the AL East in all but the 2004 season, when they finished second to last. Following the 2007 season, Stuart Sternberg, who had purchased controlling interest in the team from Vince Naimoli two years earlier, changed the team's name from "Devil Rays" to "Rays", now meaning both a manta ray and a ray of sunshine; a manta ray logo appears on the uniform sleeves while a sunburst appears on the uniform front. The 2008 season saw the Rays post their first winning season, their first AL East championship, and their first American League pennant (defeating the rival Boston Red Sox in the ALCS), though they lost to the Philadelphia Phillies in that year's World Series. Since then, the Rays have played in the postseason seven more times, winning the American League pennant again in 2020 and losing to the Los Angeles Dodgers in that year's World Series. The Tampa Bay Rays' chief rivals are the Boston Red Sox and the New York Yankees, which also play in the AL East. Regarding the former, there have been several notable on-field incidents. The Rays also have an in-state interleague rivalry with the National League (NL)'s Miami Marlins (originally the Florida Marlins), whom they play in the Citrus Series. Through 2022, the Rays' all-time record is 1,912–2,034 (.485).