T-Mobile Park: The History, the Dimensions and How the Park Plays

By 4Baseball Staff · November 5, 2026 · 11 min read

A guide to T-Mobile Park, home of the Seattle Mariners: its dimensions and retractable roof, the Kingdome years before it, how the geometry affects play and what to know before a first visit.

T-Mobile Park, home of the Seattle Mariners, has three features that most ballparks do not combine: a retractable roof that keeps rain off the seats and the field, a site only 10 feet above sea level, and power alleys in the outfield that sit within about 20 to 25 feet of the depth of center field. The park holds 47,368 fans according to the site's reference data, plays on natural grass and has been the club's home in one form or another since the middle of the 1999 season, when the team moved out of the Kingdome.

The building has had two names. It opened as Safeco Field, and the historical record lists that name for the 2000 to 2018 seasons; from 2019 it appears as T-Mobile Park. Nothing about the field changed with the name, so the history of the ballpark is the history of a single place, and this guide treats it that way. It covers the dimensions, the three homes the franchise has used in 49 seasons, the way the shape of the field affects play, the seasons that have been played in it and the practical advice that does not go out of date.

Every statistic below comes from the historical record through the 2025 season or from the site's own ballpark data. Prices, food, parking and transit are left to the club's official pages because they change every year.

The park in numbers

The table collects the reference data the site holds for the ballpark. Distances are in feet from home plate.

The five distances average about 363 feet, which sounds ordinary, but the pattern is worth a look. The two lines are short, at 331 and 326 feet, and the two alleys are longer, at 378 and 381. The jump from the line to the alley is 47 feet on the left side and 55 on the right, a real step that makes the wall bow outward between the corners. Straight-away center at 401 feet is not extreme by itself, and the alleys sit only 20 to 23 feet inside it, so the outfield wall is a long, shallow arc rather than a sharp point. As with every figure on the site, these distances are the ones listed in the site's reference data, and clubs adjust walls and fences over time, so treat them as a guide and not as a survey.

That shape is a profile for a certain kind of baseball. A pull hitter who catches a ball down the line has a short porch to aim at, while a hitter who drives the ball to the middle of the field has to hit it 70 or more feet farther than one who pulls it down the line. The outfielders cover a large amount of ground between the lines and the center-field wall, and the doubles and triples that fall between them are a normal part of the game.

Three homes in 49 seasons

The Mariners are one of the younger clubs in the American League. They joined in 1977 and, in the historical record shows through 2025, they have played 49 seasons with a record of 3,689 wins and 4,022 losses for a .478 winning percentage. In those seasons they have used two parks, with one transitional year.

The 1999 row exists because the new ballpark opened during the season. The club began 1999 in the Kingdome and finished it at Safeco Field, which is why the historical record lists both. The Kingdome was a domed concrete stadium that the club shared with football, and it was taken down in 2000 after the Mariners left. Safeco Field was the club's first purpose-built baseball home.

The attendance column shows where the club has been strongest. The best season in the building's life was 3,542,938 in 2002, which is also the franchise record, and it came the season after the 116-win year of 2001. The seven T-Mobile Park seasons through 2025 have a best of 2,690,418. Those seven seasons include 2020, a year played without fans, and the early part of 2021, when attendance was restricted. A lower best-case figure over a short span should not be read as a verdict on the building.

For the complete franchise story, including the Kingdome years and the lean seasons around them, read the history of the Seattle Mariners.

The roof and what it does and does not do

The park has a retractable roof, and the roof matters more here than in most places because Seattle has a long wet season. The structure covers the field and most of the seats when it is closed, and it allows the club to play games that would be postponed in an open park. The key detail is that the park is not a sealed dome. The roof is a canopy, the sides stay open, and the air inside is outdoor air, so the weather you feel in the seats is much closer to the weather outside than it would be in a fully enclosed stadium.

That has a few consequences. First, rain delays are rare compared with other open-air parks, and a game on a wet day is usually played as scheduled. Second, the temperature on a closed-roof night is not climate controlled; layers are still useful. Third, whether the roof is open or closed on a given day is the club's call and can change before first pitch, so the club's own pages are the right place to check.

For hitters and pitchers the roof does one more thing that is easy to miss. A field that can be covered is protected from the heaviest rain, which matters over a wet spring, and the shelter means the schedule survives weather that would wipe out games in an open park.

How the geometry affects play

A ballpark's character comes from the combination of its dimensions, its air, its wind and its foul ground. The site's reference data supplies the dimensions, the elevation and the roof status, so this section is built from those, with the caution that the net effect belongs to park factors.

Begin with the air. At 10 feet above sea level, T-Mobile Park sits about as low as a major-league park can. Dense air resists the flight of a baseball more than thin air does, so the ball does not carry the way it does in a high-altitude park, and cool air is denser than warm air, which adds to the effect. A fly ball that would leave a park at altitude can die on the track here. The ballpark has long had a reputation as a place where the ball does not carry, and the way to check the claim in any given season is to look at park factors rather than rely on the reputation.

Next, the alleys. With left-center at 378 feet and right-center at 381, a ball hit hard to either gap needs real carry to leave the yard, and a ball that lands in the gap can run to the wall. That makes doubles and triples easier to hit and makes range in the outfield valuable. A defense with fast outfielders can turn those gaps into outs; a defense with slow ones will give up extra bases.

Finally, the lines. At 331 feet in left and 326 in right, the lines are short enough that a pulled fly ball can be a home run even without great carry. With longer alleys and short lines, the hitter who pulls the ball gets more reward for a given swing than the one who drives it to the middle. That helps pull-heavy batters and means a pitcher who works inside to them is taking a different risk here than in a park with long lines.

To check any of this against results, look at park factors and at the leaders page, which shows how hitters and pitchers have actually done.

Mariners history through the park's seasons

The Mariners' best seasons have happened at Safeco Field. Their best winning percentage in the historical record is the 2001 team, which went 116-46, won the American League West and led the league. That team won the Division Series against Cleveland three games to two and lost the American League Championship Series to the Yankees, one game to four. Lou Piniella managed the club from 1993 to 2002 and won 836 of his 1,547 games, the most of any Mariners manager.

The postseason record shows a club that has reached the postseason six times and has never played in a World Series. The historical record shows list division titles in 1995, 1997, 2001 and 2025, and wild-card berths in 2000 and 2022.

Two points in that table are worth drawing out. The first is the long gap in the middle: after 2001, the club did not return to the postseason until 2022, so it missed 20 straight seasons from 2002 through 2021. The second is the 2025 series against Toronto, which went to a seventh game before the Mariners lost, four games to three. They had won the division, and it is the closest the postseason record shows the franchise coming to a pennant.

The franchise's big names are mostly connected to the ballpark in one way or another. Ken Griffey hit 417 home runs for the club between 1989 and 2010 and won the 1997 Most Valuable Player Award. Ichiro Suzuki collected 2,542 hits for the franchise from 2001 to 2019, won the 2001 Most Valuable Player Award, and was also that year's Rookie of the Year. Edgar Martinez hit 309 home runs and drove in 1,261 runs between 1987 and 2004. Felix Hernandez won 169 games and struck out 2,524 batters, both club records, and won the 2010 Cy Young Award. Randy Johnson won 130 games and struck out 2,162 for the club before the park opened. The full list, with positions, is in the best Mariners at each position, and the best seasons and every October run gives the series detail.

The neighbors in the division

Seattle plays in the American League West, and the park's seasons look different next to its division rivals. The Athletics, the Astros and the Angels are three of the four other clubs in the division, along with the Rangers. Houston is the opponent that ended the 2022 run, sweeping the Division Series three games to none. The Mariners, who have never won a pennant, play in a division where other clubs have collected several, and the three histories linked above show how different those paths were.

A point for park-minded fans is that the club's career totals mix two very different homes. Ken Griffey's 417 home runs came over 13 seasons with the club and Edgar Martinez's 309 over 18, and both careers straddle the move from the Kingdome to Safeco Field. The historical record does not split home and road totals, so this guide gives no split; a hitter's numbers in one park are best compared with the same player's road numbers from a source that carries game-by-game splits.

Planning a first visit

A guide to a ballpark is only useful if it helps you plan the day. The advice here is general, because prices and policies change, and it is the part that will still be true in a few seasons.

• Check the schedule first. The schedule page lists the home dates, and the club's own site carries the promotional schedule.
• Dress in layers. Even with the roof, the air in the seats is outdoor air. Seattle evenings cool quickly, and the open sides mean the air in the seats is outdoor air.
• Do not skip the pregame. Gates normally open well before first pitch, and the early hour is the best time to see the field and the outfield view without a crowd.
• Read the bag policy at home. The club publishes the current rules for bags and outside items, and it is easier to read them at home than at the gate.
• Plan for weather without a rain plan. A closed roof lets games go ahead in wet weather, but the way to your seat may still be wet, so a light jacket helps.
• Use the club's accessibility page. It explains the services available and how to request them in advance.
• Allow time to walk the concourse. The outfield views are part of the park's appeal, so give yourself a few minutes.

If you are bringing children, aim for a shorter plan with a clear first and last inning, and let the club's family guidance cover stroller and bag rules.

Common questions

When did the Mariners start playing at T-Mobile Park? The historical record shows list the ballpark from 1999, when the club moved from the Kingdome partway through the year, and the name T-Mobile Park appears from 2019. Before that it was called Safeco Field.

Does the park have a roof? Yes, a retractable one. It covers the field and most of the seating when closed, but the sides are open, so it is a rain shelter and not a climate-controlled dome.

Is it a pitcher's park? The elevation points that way, and the park has long had that reputation, but the actual figure is a park factor and it moves from year to year. Treat the reputation as a hypothesis and the numbers as the evidence.

How big is the park? The reference figures are 331 feet down the left-field line, 378 to left-center, 401 to straight-away center, 381 to right-center and 326 down the right-field line.

How many fans does it hold? The site data gives 47,368. Announced crowds can vary from that figure.

Has the club won a pennant? Through the 2025 season, no. The club has won four division titles and made six postseason appearances, and in 2025 it came within a game of the World Series.

Where to go next

Start with the history of the Seattle Mariners, then see how the franchise's neighbors developed in the Angels and Astros histories. For the format of the series that decide each October, the history of the World Series explains how the road to a pennant has changed. Live scores and the next game are on the Mariners team page, and the park has its own entry at T-Mobile Park; news from the club is on the Mariners topic page.