Baseball's Expansion Timeline: 1961, 1962, 1969, 1977, 1993 and 1998
How major-league baseball grew from 16 clubs to 30 in six waves between 1961 and 1998: who joined, why each wave happened, how the new clubs fared, and what expansion did to the game.
From 1901 into the 1950s the major leagues held steady at 16 clubs, eight in each league, and the map of the game changed only when a club moved. Then, between 1961 and 1998, baseball added 14 teams in six waves and reached 30. Those waves were not random. Each answered a specific pressure: a threat of a rival league, a city abandoned by its club, a lawsuit, or the simple fact that new markets were willing to pay for a team. The result is the map of the game that fans know today.
This article walks through the six waves in order, with the historical record for the season-one record of each new club and for the league sizes. It explains why each addition happened, what changed in the way the game was organized, and what happened to the new clubs. It ends with a plain account of what expansion does to statistics, because anyone comparing a 1950 player to a 1970 player is comparing eras with a different number of teams.
The six waves at a glance
The table shows each wave, the clubs added and the record each one posted in its first season, according to the historical season sheets.
| Year | League | New clubs | First-season records | Major-league clubs after |
|---|---|---|---|---|
| 1961 | American | Los Angeles Angels, Washington Senators | 70-91, 61-100 | 18 |
| 1962 | National | New York Mets, Houston Colt .45's | 40-120, 64-96 | 20 |
| 1969 | Both | Kansas City Royals, Seattle Pilots, Montreal Expos, San Diego Padres | 69-93, 64-98, 52-110, 52-110 | 24 |
| 1977 | American | Seattle Mariners, Toronto Blue Jays | 64-98, 54-107 | 26 |
| 1993 | National | Colorado Rockies, Florida Marlins | 67-95, 64-98 | 28 |
| 1998 | Both | Arizona Diamondbacks, Tampa Bay Devil Rays | 65-97, 63-99 | 30 |
Every first-season record in the table is a losing record, and most of them are very bad. That is part of the economics of expansion. A new club picks its players from the rosters of the existing clubs, which are allowed to protect most of their best players, so the first roster is built from what is left. It takes years to build a competitive team from that, and some clubs take much longer than others.
A note on counting: the 1961 Senators in the table are the second Washington club. The original Senators moved to Minnesota after the 1960 season and became the Twins, and the American League placed a new club in the capital. That is why the 1961 sheet lists both a Minnesota Twins club (70-90) and a Washington Senators club (61-100).
1961 and 1962: the lawsuit, the rival league and the empty cities
Expansion in the early 1960s followed the biggest relocation in the history of the sport. After the 1957 season the Dodgers left Brooklyn and the Giants left Manhattan, and New York, the largest city in the country, had no National League team. That story is told in its own article. What matters here is what it set off: a group led by William Shea, with the former executive Branch Rickey as president, announced plans for a third major circuit, the Continental League, to place clubs in New York and other cities without a team. The existing leagues did not want a rival, and the way to defuse it was to give those cities franchises of their own.
The American League moved first. For 1961 it placed a new club in Los Angeles, a market the National League had just claimed with the Dodgers, and a new club in Washington to replace the departed Senators. The league also lengthened its schedule from 154 games to 162. The National League followed for 1962 with the Mets in New York and the Colt .45's in Houston, and it too moved to 162 games.
The historical season sheets show the first results. In 1961 the new Los Angeles Angels went 70-91, a respectable start for an expansion club, finishing eighth in the ten-club American League and ahead of both the Kansas City Athletics and the new Washington club, which went 61-100. In 1962 the Mets finished 40-120, the worst record in the sheets for any of the 20 clubs, and the Colt .45's went 64-96, finishing eighth ahead of the Cubs and the Mets. The Mets' season has been remembered as a joke, and seven years later the club won the World Series.
Note what the 1961 sheet says about the game. Runs per team-game were 4.53, up from 4.31 in 1960, and home runs per team-game were 0.95, up from 0.86. Roger Maris hit 61 home runs, and the 162-game schedule made his total a subject of debate, since the old record had been set in a 154-game season. A plausible part of the increase is that the new clubs filled their pitching staffs with pitchers who might not otherwise have been in the majors. The effect was real, but it should not be overstated: the difference in runs per game between 1960 and 1961 is about a fifth of a run.
1969: four clubs, two divisions and a lower mound
The third wave was the largest. For 1969 the American League added Kansas City and Seattle, and the National League added Montreal and San Diego, and both leagues split into two six-team divisions, East and West, with a league championship series to decide the pennant. The historical record 1969 sheet shows the new arrangement: the American League East and West, and the National League East and West, each with six clubs.
The reasons were several. Kansas City had lost its club after the 1967 season, when the Athletics moved to Oakland, and political pressure from the state of Missouri led the American League to promise a replacement; the Royals were the answer. Seattle received the Pilots, who played one season in 1969 with a 64-98 record and became the Milwaukee Brewers the following year. The National League chose Montreal, the first major-league club outside the United States, and San Diego. Both new National League clubs went 52-110 in their first season, tied for the worst record in the majors that year.
The Mets, meanwhile, finished the 1969 season with 100 wins and 62 losses, won the National League East and swept the Braves in the league championship series, and beat Baltimore in the World Series, four games to one. A club that had lost 120 games seven years earlier was world champion. It is the best-known turnaround in the history of expansion, and it is also a reminder that talent can arrive quickly when a club drafts and trades well.
The year is also remembered for a rule change unrelated to expansion. The pitcher's mound was lowered and the strike zone reduced for 1969, after a 1968 season in which teams scored an average of only 3.42 runs per game. In 1969, with new clubs diluting the pitching and the rules shifting toward hitters, the figure rose to 4.07 and home runs per team-game rose from 0.61 to 0.80. Both effects are visible in the same numbers, and they cannot be separated cleanly. The story of the Montreal club is in its own article.
1977: Seattle and Toronto
The American League added Seattle and Toronto for 1977, taking it to 14 clubs and the majors to 26. Seattle's return was driven by its loss of the Pilots: the city and state took the league to court, and an American League that had left the city after a single season agreed to return. Toronto, the second Canadian city in the majors, received the other club.
The first records were hard. The Mariners went 64-98 and finished sixth in the American League West, and the Blue Jays went 54-107, last in the American League East. The league's standings for 1977 show the shape of the competition: the Yankees won the East at 100-62 and the Royals the West at 102-60, and the Yankees beat the Dodgers in the World Series, four games to two.
The long-term outcomes differed. The Blue Jays became one of the most successful expansion clubs in the sense of titles, winning the World Series in 1992 and 1993, the first non-American club to win it. Their best season attendance, 4,057,947, came in 1993 at the Skydome. The Mariners, in contrast, have never won an American League pennant according to the database, through the 2025 season. The Mariners' first park, the Kingdome, was used from 1977 until partway through the 1999 season.
Another point: the Royals, expansion children of 1969, won the American League West at 102-60 in 1977, only their ninth season. They won the pennant in 1980 and 1985 and the World Series in 1985, a reminder that the time it takes to build a winner varies.
1993: Denver and Miami
Sixteen years passed before the next wave. The National League added the Colorado Rockies and the Florida Marlins for 1993, taking the majors to 28 clubs and each league to 14. The 1993 sheet shows the state of the game that year: seven clubs in each division, with the Blue Jays and the Phillies winning the pennants and Toronto beating Philadelphia in the World Series, four games to two.
The new clubs were both an immediate hit with fans. The Rockies played their first two seasons at Mile High Stadium, and the database shows their best season attendance, 4,483,350, in 1993, the first year, in that building. The Marlins drew 3,064,847, their best in the database, in 1993 as well. Newness sells tickets, and both clubs spent the rest of their histories trying to recapture the crowds of that first summer.
The on-field results were more typical. The Rockies went 67-95 and the Marlins 64-98. In 1997, only their fifth season, the Marlins won the World Series as a wild-card team, beating Cleveland four games to three. They won again in 2003. The Rockies reached the World Series in 2007 and lost, and have not won a title through 2025. The Colorado club also introduced a new problem to baseball: Denver sits at high elevation, and the thin air changes how the ball behaves. The park's effect on offense and pitching has been a subject of study ever since.
The clubs' arrival coincided with a larger reorganization. The sport moved to three divisions per league in the strike-shortened 1994 season, and in 1995 added a wild card, which meant that the number of postseason teams rose from four to eight. The 1998 sheet shows the new structure: three divisions per league, labelled East, Central and West, and a wild-card club in each league.
1998: Phoenix and Tampa Bay
The last wave, so far, came in 1998. The National League added the Arizona Diamondbacks and the American League added the Tampa Bay Devil Rays, taking the majors to 30 clubs. To keep the leagues in balance, the Milwaukee Brewers moved from the American League to the National League, which is why Milwaukee appears in the 1998 sheet in the National League Central. That put 16 clubs in the National League and 14 in the American. The arithmetic explains the choice: with an odd number of clubs in a league, one club is idle every day unless interleague games are scheduled all season, so two leagues of 14 and 16 are easier to schedule than two of 15. The imbalance lasted until the Houston Astros moved to the American League in 2013.
The records for 1998 were typical of expansion clubs: the Diamondbacks went 65-97 and the Devil Rays 63-99. But the Arizona club moved faster than most. The database lists the Diamondbacks' World Series title in 2001, only their fourth season. It was a very fast rise for an expansion club. Their best season attendance, 3,610,290, came in their first year, 1998, at Bank One Ballpark, a pattern now familiar.
The 1998 season is remembered for other reasons. Runs per team-game averaged 4.79 and home runs per team-game reached 1.04, the highest figure among the sheets in this article, and Sammy Sosa won the National League MVP award in the season that he and Mark McGwire chased the home run record. The Yankees went 114-48 and swept the Padres in the World Series. Expansion may have thinned the pitching again, and explanations offered for the surge also include smaller strike zones, smaller parks and stronger hitters. Again, the causes cannot be cleanly separated.
What happened to the new clubs
The expansion clubs have had very different histories. The table lists the World Series titles in the historical record, through the 2025 season.
| Club | First season | World Series titles |
|---|---|---|
| Mets | 1962 | 1969, 1986 |
| Astros (Colt .45's) | 1962 | 2017, 2022 |
| Royals | 1969 | 1985, 2015 |
| Padres | 1969 | None (pennants in 1984, 1998) |
| Blue Jays | 1977 | 1992, 1993 |
| Mariners | 1977 | None (no pennants) |
| Marlins | 1993 | 1997, 2003 |
| Rockies | 1993 | None (pennant in 2007) |
| Diamondbacks | 1998 | 2001 |
Two lessons come out of the table. First, expansion clubs can win quickly, since the Mets did it in eight years and the Diamondbacks in four, and they can also wait: the Astros took 55 years to win their first championship, and the Padres and Mariners have not won one. Second, nothing about the date of arrival predicts the outcome: the Mariners and the Blue Jays joined together in 1977, and their histories are very different.
Other clubs from these waves, the Angels, the second Senators (who became the Texas Rangers) and the Brewers, also have histories, but their records are covered in their own franchise articles. Readers who want the whole picture of how clubs moved and changed names, a different kind of change from adding clubs, can read Teams That Moved.
What expansion does to statistics
Adding clubs changes the sport in at least four ways that a fan should keep in mind.
- Talent dilution. If the number of roster spots rises faster than the pool of talented players, the average quality of play can fall. Defenders of expansion point out that the population grew and the sport recruited internationally; critics point to the weak early records of new clubs. The honest answer is that it is hard to measure, and the effect is probably small relative to the other changes of the era.
- Schedule length. The move from 154 to 162 games in 1961 and 1962 changed what a record season meant, and the Maris debate was a result.
- Structure. Divisions, league championship series and wild cards all followed expansion. A pennant race among six clubs in a division is different from a race among eight or ten, and the arithmetic of magic numbers applies within the division.
- Sample size. New clubs produce new players with short records, and statistics in the first years of an expansion club are noisy. Sample size and regression to the mean explain why a player's first-year numbers on a bad club may mislead.
Compare the shape of the two ends of the timeline in the sheets: in 1961, 18 clubs scored 4.53 runs per team-game, and in 1993, 28 clubs scored 4.60. The scoring level ended up in nearly the same place after three decades and ten new clubs, though it swung widely in between, from 3.42 in 1968 to 4.79 in 1998. Expansion alone does not explain scoring, and anyone who says it does is leaving out the mound, the strike zone and the parks.
The people who ran the sport also changed. Ford Frick was commissioner during the 1961 and 1962 waves, and Bud Selig was the owners' leader through 1993 and 1998. The line of office is covered in the article on commissioners. The owners' labor fights of the 1980s, which preceded the 1993 wave, are described in the collusion article.
Common questions
How many teams were added from 1961 to 1998? Fourteen: two each in 1961, 1962, 1977, 1993 and 1998 and four in 1969. That is how the majors grew from 16 clubs to 30.
Has baseball expanded since 1998? As of the 2025 season, the database shows no new club added since the Diamondbacks and Devil Rays. Talk of further expansion changes from year to year, so check the league's official site for the current status.
Which expansion club was the worst in its first season? The Mets of 1962, at 40-120, according to the historical season sheet. The 1969 Expos and Padres, each at 52-110, were the next worst of the clubs listed here.
Why did the Brewers change leagues? In 1998, adding one club to each league would have produced two leagues of 15, which leaves one club idle every day without constant interleague play. Moving Milwaukee to the National League produced leagues of 14 and 16 instead.
Did the divisions begin with expansion? The two-division format began in 1969 with the four new clubs, and the three-division format began in 1994 and was followed by the wild card in 1995, after the 1993 wave.
Where to go next
If you want the stories of the clubs themselves, start with the Dodgers and Giants moving west and the Montreal Expos, which explain two of the big forces behind the waves. For the arithmetic of the pennant races that the new divisions created, read magic numbers explained, and for current standings, check the standings page. You can also browse business and labor for more on the owners and the league structure.