Following the Nats' sweep of the St. Louis Cardinals in the National League Championship Series, the Mariners are now the only active team in Major League Baseball without an appearance in the World Series.
The Mariners have made the playoffs just four times since the franchise's inception in 1977 and are currently mired in an 18-year drought. Seattle has advanced to the championship series three times in those four postseason appearances, going 5-12 and never forcing a Game 7.
The Nationals entered the majors as the Montreal Expos in 1969. Playing as the Expos until 2004, the club made the playoffs once, winning one playoff series before being booted by the Los Angeles Dodgers in the 1981 NLCS. After relocating from Montreal, the Nationals made the postseason on four occasions prior to 2019, losing in the divisional round each time.
The Washington Senators won three pennants - including one World Series victory in 1924 - during their tenure in the league. The franchise relocated following the 1960 campaign to become the Minnesota Twins.
Seattle's only other MLB franchise, the Pilots, played only one season in 1969, finishing last in the majors before declaring bankruptcy during spring training the following season. The franchise relocated to Wisconsin to become the Milwaukee Brewers.
Should the Nationals go on to win the Fall Classic, the Mariners will still have some company on the list of teams without championships; the Brewers, Tampa Bay Rays, San Diego Padres, Texas Rangers, and Colorado Rockies have also failed to claim the Commissioner's Trophy.