When the Major leagues first expanded in 1961, two teams- The Los Angeles Angels and Washington Senators-were added. Many people think that the Minnesota Twins were an expansion team, but they were originally the first version of the Senators. After they moved to Minnesota, the AL decided to expand, and a second Senator team was formed. After eleven, mostly unsuccessful years, the team moved to Arlington Texas, and became the Rangers. The next year, the National League also expanded, with the senior circuit getting a team in New York after four years without one...the Giants and Dodgers having moved West in '58. The other team was the Houston Colt '45s, who had spent the first three years of their existence playing in an outdoor stadium, only to change their venue and name in 1965, to the Astrodome and Astros, respectively.
As confusing as the first expansion was, the second may have been even more so. 1969 saw four new teams added, two from each league: The San Diego Padres and Montreal Expos in the National League, and the Kansas City Royals and Seattle Pilots in the American League. Obviously, two of these teams don't exist anymore. The Expos had a good run, though, lasting 35 years, making the NLCS in 1981, the best record in baseball in the other strike shortened season in 1994, and producing two (soon to be three) Hall of famers. (Gary carter is the only player to go to Cooperstown wearing an Expos cap, while Andre Dawson- who actually spent a lot more time playing for Montreal than any other team-went in wearing a Cubs cap. The Expos became the Washington Nationals in 2004.
So, that just leaves the Pilots, easily the most obscure team of the last 100 years. The Pilots played their one season in tiny Sicks stadium, which was the former home of the minor league "Seattle Rainers" (get it?), which only held 19,500 fans, although they ended up adding 6,500 more by opening day. The most famous person on the club may have been Jim Bouton, who, by that point was strictly a reliever. He talks about his one year with that team in his book "Ball Four." Mike Hegan was the lone Seattle player selected for the All star game, but was injured, so team mate Don Mincher took his place. Another player, speedster Tommy Harper, would have some good years with the Milwaukee Brewers and Boston Red Sox in the early '70s. '
Of course, it was Milwaukee where the team moved the next year, thanks to local resident, and future Baseball commissioner Bud Selig. There wouldn't be another team in Seattle until the next expansion, in 1977. The Seattle Mariners are the only American league franchise left who have never won a pennant. The only N.L. team never to win one is/are the Expos/Nationals. The Mariners have had some success, though, making it to the ALCS twice (in '95 and '01), and at least two of it's players-Ichiro and Ken Griffey Jr.- will most likely go into the Hall of fame wearing a Seattle cap.
The Pilots are but a footnote, now, mostly being mentioned as part of the history of the Brewers...however, even though they only had one season-a season where they finished last in the newly formed A.L. West at 64-98-they served as lesson to be learned for anyone trying to bring a team to their city. For one thing, they had rather high ticket prices for an expansion team who played in a run down old minor league park. Also, they were all set to start the 1970 season as the Pilots, until several circumstances led them to become the Brewers on April 1st, 1970...APRIL 1st, as in only days before the season began. Guess Selig really wanted a team in his hometown...oh, if that were the only thing in baseball he did...