The Athletics (often referred to as the A's) are an American professional baseball team based in West Sacramento, California. The Athletics compete in Major League Baseball (MLB) as a member club of the American League (AL) West Division. The team will play its home games at Sutter Health Park in West Sacramento for the 2025–2027 seasons before its planned relocation to the Las Vegas metropolitan area. While in West Sacramento, the team is being referred to as simply the "Athletics" and "A's", with no city name attached. The franchise's nine World Series championships, fifteen pennants, and seventeen division titles are the second most in the AL after the New York Yankees. One of the AL's eight charter franchises, the team was founded in Philadelphia in 1901 as the Philadelphia Athletics. They won three World Series championships in 1910, 1911, and 1913, and back-to-back titles in 1929 and 1930. The team's owner and manager for its first 50 years was Connie Mack, and Hall of Fame players included Chief Bender, Frank "Home Run" Baker, Jimmie Foxx, and Lefty Grove. The team left Philadelphia for Kansas City, Missouri, in 1955 and became the Kansas City Athletics, before moving to Oakland, California, in 1968 and becoming the Oakland Athletics. The Athletics played their home games at the Oakland Coliseum from 1968 until 2024. Nicknamed the "Swingin' A's", under owner Charlie O. Finley they won three consecutive World Series in 1972, 1973, and 1974, led by players including Vida Blue, Catfish Hunter, Reggie Jackson, and Rollie Fingers. After being sold by Finley to Walter A. Haas Jr., the team won three consecutive pennants and the 1989 World Series behind the "Bash Brothers", Jose Canseco and Mark McGwire, as well as Hall of Famers Dennis Eckersley, Rickey Henderson and manager Tony La Russa. In 2002, the Athletics set a then American League record for most consecutive wins in a season with twenty, an event that would go on to be the pioneering step in the application of sabermetrics in baseball. The streak record was later broken in 2017 by the Cleveland Indians. From 1901 through the end of 2024, the franchise's overall win–loss record is 9,329–9,859–87 (.486).

Sutter Health Park

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.