The Green Monster is the left-field wall at Fenway Park. The Red Sox list it at 37 feet high and 231 feet long (228 feet of it in fair territory), standing 310 feet from home plate at the foul line (Red Sox: Facts and Figures). It was not built to fix a short left field. MLB.com’s history says the first version, a 25-foot wooden fence in 1912, was built to keep non-paying fans from watching from buildings on Lansdowne Street (MLB.com: Why does Fenway have the Green Monster?).
The numbers, from the team
| Measurement | Figure |
|---|---|
| Left field wall height | 37 ft |
| Wall length | 231 ft (228 ft in fair territory) |
| Distance to the wall at the left-field line | 310 ft |
| Left-center / center / deep center | 379 ft / 390 ft / 420 ft |
| Other wall heights | Center 17 ft, bullpens 5 ft, right field 3–5 ft |
| Seats on top of the wall | 269 |
Source: Red Sox Facts and Figures, checked October 3, 2026. Other parks are on our outfield walls compared page.
Why was the wall built?
The story begins with Fenway’s opening in 1912. According to MLB.com, owner John I. Taylor noticed that buildings on Lansdowne Street were tall enough for people to watch from windows and rooftops, so he built a 25-foot wooden fence from beyond the left-field foul pole to the center-field flagpole to make everyone buy a ticket. An embankment in front of it, nicknamed Duffy’s Cliff, gave overflow crowds extra seating (MLB.com).
How the wall became the Green Monster
- 1934: After a fire in 1933 destroyed much of the park, the wall was rebuilt with a concrete base and the hand-operated scoreboard that is still in use.
- 1936: A 23-foot net was installed above the wall to keep home runs from damaging businesses on Lansdowne Street.
- 1947: The advertisements that had covered the wall since the first game were removed and the wall was painted the same green as the rest of the ballpark, which is where the nickname comes from.
- 2003: The nets came down and 269 seats went on top of the wall.
All four dates are from MLB.com’s history of the wall.
What the numbers do to the game
A ball hit down the left-field line has to travel only 310 feet to reach the wall, but it must also be high enough to clear 37 feet. A ball that hits the wall stays in play. Fenway’s other fences are far lower: 17 feet in center, 3–5 feet in right. There is no single “how far to hit it over the Monster” number, because the distance depends on where along the wall the ball goes; the Red Sox list 310 feet at the line and 379 feet in left-center.
For the history of other park features, see Wrigley Field’s ivy walls.
Frequently asked questions about the Green Monster
How tall is the Green Monster at Fenway Park?
37 feet, according to the Red Sox. The wall is 231 feet long.
How far is the Green Monster from home plate?
310 feet at the left-field foul line; the Red Sox list 379 feet to left-center.
Why is it called the Green Monster?
In 1947 the ads that had covered the wall were removed and it was painted green, matching the rest of the park.
Can you sit on top of the Green Monster?
Yes. 269 seats were added on top of the wall in 2003, when the nets came down.
Why was the wall built?
MLB.com says the original 25-foot wooden fence of 1912 was built to keep people on Lansdowne Street from watching for free. The concrete-based wall with the hand-operated scoreboard dates from the 1934 rebuild after a fire.
Reviewed against primary sources on October 3, 2026. We rewrote this article that day. The earlier version said the wall was built to offset a short left field and gave the height only as “thirty-plus feet”; the sources above give the height exactly and a different reason for the first fence. Sources: Red Sox: Facts and Figures · MLB.com: Why does Fenway have the Green Monster?. Drafted with AI assistance; see our editorial policy.
Related reading
Ballpark outfield walls compared, Wrigley Field’s Ivy Walls: A History, Baseball Superstitions Players Actually Believe, The Seventh-Inning Stretch: History of a Tradition.