Domed Stadiums and the Astrodome: How Baseball Moved Indoors
How the Houston Astrodome of 1965 put major-league baseball under a roof, why grass gave way to artificial turf, and what the Kingdome, Metrodome and later roofed parks did to the game.
For most of its first century baseball was a sport you watched in the open air. If it rained, you waited, and if it was hot, you sweated. In 1965 that changed when the Houston Astros opened the first major-league ballpark with a roof over the entire field. The Astrodome was a building so unusual that its builders reached for superlatives, and the problems it created, from a glare that hid fly balls to grass that would not grow, led to another invention that reshaped the sport for a generation: artificial turf.
This article follows the idea from its beginnings in a hot, mosquito-ridden Texas summer through the domes of Seattle, Minneapolis, Toronto and Tampa to the retractable roofs that replaced them. It uses the historical record for which club played where and when, and for a comparison of scoring in the roofed parks. It also covers what a roof does to the game itself, which is less than people assume in some respects and more in others.
Why Houston needed a roof
Houston received a National League club for 1962, and the Houston Colt .45s needed a place to play before their permanent park was built. They used Colt Stadium, an open-air temporary ballpark, from 1962 through 1964 according to the historical record shows, and the best season attendance there was 924,456. Houston in summer is hot and humid, and the stadium was also remembered for mosquitoes. A club hoping to build a fan base in that climate had a strong incentive to find a way to put the game in air-conditioned comfort.
The man who pushed the idea was Roy Hofheinz, a former mayor of Houston and county judge who was one of the club's owners. His plan was for an enclosed stadium with a roof and air conditioning, built in Harris County. The building was formally the Harris County Domed Stadium, and it became known by the name the club adopted when it renamed itself: the Astros, a reference to Houston's role in the American space program, with the park as the Astrodome.
The historical record shows show the Astrodome as the Astros' home park from 1965 through 1999, a run of 35 seasons, with a best season attendance of 2,706,017. The first game in the building was an exhibition against the New York Yankees in April 1965, and Mickey Mantle is credited with the first home run hit there. The regular season began a few days later.
The building and its first problem
The Astrodome was designed to impress, and it did. It was described in its own publicity as the Eighth Wonder of the World, a phrase that said as much about the owner as about the building. The roof was made of many translucent panels, because the designers wanted natural grass inside, and grass needs sunlight.
That choice caused the first trouble. During the day, the light through the panels created a glare that made it hard for outfielders to follow a high fly ball against the roof. Players were reported to have lost balls in the glare, and the club responded by painting the panels to cut the light. The paint solved the problem for the fielders and created another one for the field, because the grass in the building began to die.
By the middle of the 1960s the Astros had a baseball field with brown, dead turf. The solution was to replace the grass with a synthetic surface. The product was made by the Monsanto company, and in the Astrodome it became known as AstroTurf. The 1966 season was the first with the artificial surface, and by the middle of that season the whole field was covered. A surface invented for a stadium that could not grow grass became the most important piece of equipment the building produced.
The turf era
Artificial turf spread because it solved other problems. It is durable, it drains quickly, and it can be used for football and baseball in the same building without the field being torn up. In the early 1970s several new multi-purpose stadiums, including those in Cincinnati, Pittsburgh and Philadelphia, were built with artificial surfaces.
The surface changed how the game was played. A ground ball on turf travels faster and bounces higher than on grass, so infielders had to play deeper and range farther, and the balls that got through the infield went through for hits more often. Outfielders had to play deeper to keep a bouncing ball from going over their heads, and the faster surface produced extra-base hits that grass might have held to singles. The most visible beneficiary was the fast runner. A club that wanted to win on turf built a team of fast outfielders and good infielders, with a premium on stolen bases and defense, and the St. Louis Cardinals of the 1980s under manager Whitey Herzog are the standard example of the approach.
The turf had critics. Players complained about the hardness of the surface and about how hot it could become, and the debate about injuries has never been fully resolved. The trend later reversed, as new ballparks returned to natural grass.
What the Astrodome did to scoring
A roof does not change the weather, but it does change the park. The Astros have a record that suggests the Astrodome favoured pitchers. The table below compares the average combined runs and home runs per game in the club's games with those of the whole major leagues in the same years. All figures are derived from the historical record. Because it includes road games, the effect at home would be about twice as large, and because a club's own roster affects the numbers, it can only suggest a pattern.
| Park (club) | Seasons | Runs per game in club's games | Runs per game in all games | Home runs per game in club's games | Home runs per game in all games |
|---|---|---|---|---|---|
| Colt Stadium (Astros, open air) | 1962-1964 | 7.28 | 8.30 | 1.13 | 1.74 |
| Astrodome (Astros) | 1965-1999 | 8.18 | 8.64 | 1.33 | 1.66 |
| Kingdome (Mariners) | 1977-1998 | 9.33 | 8.88 | 1.94 | 1.72 |
| Metrodome (Twins) | 1982-2009 | 9.44 | 9.23 | 1.96 | 1.94 |
| Tropicana Field (Rays) | 1998-2024 | 9.00 | 9.17 | 2.16 | 2.18 |
Two things stand out. First, the Astros' games were low-scoring both at Colt Stadium and in the Astrodome, so some of the effect belongs to the club and its pitchers, and the Astrodome years are best read as a modest reduction. Second, the other domes do not follow the pattern. Games involving the Mariners in the Kingdome were higher scoring than average, with many more home runs. Games involving the Twins in the Metrodome were close to average. The Rays' games at Tropicana Field were also close to average, and their home runs per game were almost exactly the league figure.
That is the main point about roofs: no roof makes a park a pitcher's park or a hitter's park. The dimensions, the surface and the air do that. A roof only removes the weather.
The Kingdome and the Metrodome
Seattle's Kingdome was a concrete dome that opened in 1976, and the Mariners played their home games there from their first season in 1977 through 1998, with a partial overlap in 1999 in the historical record shows. It was a multi-sport building, shared with football, and it was known more for its function than its charm. In 1994 ceiling tiles fell from the roof before a game, an incident that led to the club playing an extended period on the road while the building was inspected. The Kingdome was replaced by Safeco Field, a ballpark with a retractable roof that opened in 1999, and the Kingdome was demolished in 2000.
Minneapolis had the Metrodome, the home of the Twins from 1982 through 2009 in the historical record shows. Its roof was an air-supported fabric held up by air pressure, rather than a rigid structure, so it required a constant flow of air to stay inflated. It was white, which made high fly balls hard to see, and it had a reputation for loud crowds. The Twins won the World Series there in 1987 and 1991, and in both series the home team won every game, a statistic that fans in the building remembered. The roof also failed under heavy snow in December 2010, after the Twins had left, causing it to deflate.
The Twins moved to the open-air Target Field in 2010, and the historical record shows list it as their home through 2025. The change was a statement about what a dome cost: a stadium with no sky. The two championship runs fit into the wider story of how the MLB postseason works.
Montreal, Toronto and Tampa Bay
Other domes served clubs in cities with cold or wet weather. The Montreal Expos moved from Jarry Park to Olympic Stadium, listed as Stade Olympique in the historical record shows from 1977 through 2002, with a small part of 2003 and 2004 played in Puerto Rico. The stadium had been built for the 1976 Olympics, and its planned retractable roof never worked as designed. The story of the club and its park is told in the Montreal Expos article.
Toronto's SkyDome opened in 1989 with a fully retractable roof, the first of its kind for a major-league park, and the Blue Jays have played there since, under the name Rogers Centre since 2005 in the historical record shows. The roof opens in good weather and closes in bad, which gives the club the best of both options.
The Tampa Bay Devil Rays began play in 1998 in what is now called Tropicana Field, a fixed dome with catwalks high in the roof that are part of the ground rules. The historical record lists the club at Tropicana Field through 2024. For 2025, the record lists Steinbrenner Field in Tampa as the club's home, after storm damage to the dome's roof. The fixed dome was a conservative choice in a rainy climate, and it made Tampa Bay one of the clubs most dependent on a single building.
The retractable-roof generation
The last quarter of the twentieth century produced a different idea: a roof you can open. The Arizona Diamondbacks started in 1998 at Bank One Ballpark, now Chase Field. The Mariners' Safeco Field followed in 1999, Houston's Enron Field in 2000 (now Minute Maid Park, and listed in 2025 as Daikin Park), Milwaukee's Miller Park in 2001 (now American Family Field), and the Marlins' ballpark in Miami in 2012. Texas added its own in 2020.
The reasoning is simple. Phoenix, Houston and Miami are hot and wet places where a closed roof and air conditioning serve fans for much of the season. Seattle and Milwaukee are places where rain and cold are the problem, and a roof lets the club keep a schedule. In good weather the roof opens and the game is played in the air. This is the compromise that replaced the sealed dome, and it is why the Astrodome has no direct heirs.
The Astrodome itself closed to baseball after 1999. The club moved to Enron Field in 2000 and played in a park with a retractable roof, grass and a more traditional ballpark design. The old building remained as a landmark and was used for other events, such as the 1973 tennis match between Billie Jean King and Bobby Riggs.
What a roof changes, and what it does not
The roof gives a baseball game three things, and costs it two.
- Certainty. Rainouts and delays vanish, and a fan can buy a ticket without checking the forecast. Clubs can plan promotions and television schedules with confidence.
- Comfort. Air conditioning makes July in Houston or Phoenix tolerable.
- Constant conditions. No wind, no cold, no sun in a fielder's eyes, though the roof itself can cause problems with fly balls, as the white Metrodome and the catwalks at Tropicana Field show.
The costs are the loss of the weather and the sky, which many fans value, and the usual need for a surface that grass cannot always provide. The turf era was in part a result of domes, and its end was in part a result of retractable roofs, which can let in enough light to grow natural grass.
The late twentieth-century trend toward retro-style ballparks, led by Camden Yards in Baltimore in 1992, emphasised open air and grass, and that set the tone for the clubs that followed. The roofed parks that remain are mostly retractable.
Common questions
Which was the first domed stadium in the major leagues? The Houston Astrodome, which the historical record shows as the Astros' home from 1965 to 1999.
Why was the Astrodome's grass replaced? The translucent roof panels created a glare, the panels were painted to reduce it, and the grass that depended on that light died. The club switched to artificial turf, which became known as AstroTurf.
Do domes always favour pitchers? No. The Astros' games suggest a modest pitching advantage, but games in the Kingdome favoured hitters and games in the Metrodome and Tropicana Field were close to average.
What happened to the Kingdome? The Mariners left it for Safeco Field, which opened in 1999, and it was demolished in 2000.
Are today's roofed parks sealed domes? Most of the roofed major-league parks built since the late 1990s have retractable roofs. Tropicana Field was long the fixed-dome exception; the historical record shows list the Rays there through 2024 and elsewhere in 2025, so check the club's official site for its current home before planning a visit.
Where to go next
If the history of moving ballparks interests you, read how the Montreal Expos ended up in Washington and the story of clubs that changed cities. To see how the games played under these roofs fit into October, the postseason guide explains the current format. Each club's current home is on its team page, and the ballparks and fans topic page collects more stadium coverage.